AC 91-70B

Historical

Advisory circular · Oceanic and Remote Continental Airspace Operations

A newer version is currentThis is a historical version. AC 91-70D is the version in force, approved April 3, 2025.
Approved
October 4, 2016
Last reviewed
August 2, 2024
Cancels
AC91-70A
Cancelled by
AC91-70B CHG 1
Family
AC 91-70 · 6 versions
Revision
B
14 CFR parts
91, 119, 121, 125, 135

Guidance, not mandatory unless a rule or AD requires it. DRS record last changed November 21, 2025.

Show pages 13–24

4.2.4.2 RSP 400 requires a 99 percent probability (continuity) the surveillance transaction will complete in less than 400 seconds (timeline). It also requires a 99.9 percent probability the communication can be initiated (availability) and no more than 10-5 communications transaction malfunctions per flight-hour (integrity).

4.2.4.3 For additional details, please see ICAO Document 10037, Global Operational Data Link Document (GOLD, current edition), Appendix C, RSP Specifications.

4.2.5 Access to Performance-Based Routes. The communications, navigation, and surveillance capabilities of your crew and equipment determine your eligibility for OpSpec/MSpec/LOA authorizations that enable you to take advantage of the performance-based routes in oceanic and remote continental airspace. The significant improvements in communications, navigation, and surveillance systems have allowed air traffic controllers to reduce separation between aircraft, expanding access to the routes that offer you the maximum savings in time and fuel.

Note: For a list of pertinent OpSpecs/MSpecs/LOAs, please see Appendix B, Special Areas of Operation and OpSpecs/MSpecs/LOAs.

4.3 Voice Communications in Oceanic and Remote Continental Airspace.

ICAO Annex 6 (all three parts) requires those airplanes operating under IFR to have installed and approved radio communication equipment capable of conducting two-way communications at any time during the flight. When operating over the high seas, ICAO Annex 2 requires you to equip your aircraft with a functioning two-way radio, to establish two-way radio communications with the appropriate air traffic control (ATC) unit, and to maintain a continuous listening watch on the appropriate radio frequency.

Note: It is not acceptable to depend solely on radio relay operations to satisfy this requirement. The appropriate authority for the airspace where you conduct the flight may prescribe the aeronautical stations and frequencies used for two-way communications.

4.3.1 High Frequency (HF) Radio Communications. HF radios have been in use for almost a century over oceanic and remote continental areas. As technological advances lead to more sophisticated methods of communication, HF equipment has also improved.

HF radios now offer digital tuning, compact size, Selective Calling (SELCAL) systems (see below), and new antenna concepts. Consider the following when using HF communications:

4.3.1.1 HF radio calls are normally relayed electronically, via keyboard and display, to air traffic controllers by a radio operator. There is often a delay between your requests and ATC clearance. The radio operator does not have the authority to approve your request and must coordinate with the appropriate controller for that approval.

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4.3.1.2 Communications over HF radio rely heavily on proper radio terminology and scripted reports. Use the published guidance found in en route publications or the Aeronautical Information Manual (AIM) to make sure you deliver messages in the proper format. Speak at a moderate speed using the internationally accepted phraseology. You may find ICAO standard phraseology in ICAO Document 9432, Manual of Radiotelephony. This document and other ICAO reference materials can be found on the Publications page on ICAO’s Web site, www.icao.int.

4.3.1.3 If ATC uses the terms “expect” or “when are you able,” they have not granted you a clearance. Typically, oceanic radio operators will use the phraseology “ATC clears…” when relaying a clearance.

4.3.1.4 You must read back every clearance received from ATC. Ensure that ATC acknowledges your exact read back to confirm that you correctly heard the instructions.

4.3.1.5 In general, higher frequencies (above 10.0 megahertz (MHz)) work better during daylight and lower frequencies (below 10.0 MHz) at night. It is not uncommon to use several frequencies on one flight while communicating with the same ATS provider.

4.3.1.6 HF communications are dependent on transmitted signals striking the ionosphere and reflecting back to antennae at ground stations. The ionosphere is susceptible to interference from space weather, resulting in periods where HF reception is marginal or unreadable. You may especially notice this phenomenon in polar regions above 60° north or below 60° south and during periods of significant solar activity.

4.3.2 SELCAL. SELCAL is a means to alert an individual aircraft that a ground station wishes to communicate with it. ATS providers can transmit SELCAL signals over very high frequencies (VHF) or HF. The signals produce an audio tone and possibly a cockpit light or message that alerts you to initiate contact with the appropriate ATC unit.

4.3.2.1 The SELCAL codes are controlled by a commercial service and are assigned to a specific aircraft. Since the number of unique SELCAL codes is less than the number of aircraft with SELCAL capability, multiple aircraft could be operating and logged in with the same SELCAL code assignment.

4.3.2.2 When you apply for SELCAL codes for your aircraft, the issuing company will deconflict duplicate codes by region as much as possible. However, aircraft flying in multiple regions may encounter another aircraft using the same code. You must ensure that the SELCAL contact you respond to is intended for your aircraft.

4.3.2.3 Efforts are underway to increase the number of codes by expanding the number of audible tones that make up the system. The newest SELCAL equipment will use alphanumeric instead of the alpha-only codes, increasing 4-4

the number of unique identifiers from the current 10,920 to 215,760.

Implementation of the new system is expected to begin in the 2017 timeframe.

Operators with HF SELCAL systems not compatible with the new alphanumeric codes may continue to encounter other aircraft with duplicate codes.

4.3.2.4 Check HF SELCAL even when your Controller-Pilot Data Link Communication (CPDLC) is working properly. You should do a SELCAL check prior to oceanic entry and then again at each control area boundary.

4.3.3 SATVOICE. In keeping with ICAO’s recognition of SATVOICE as a valid Long-Range Communication System (LRCS), the FAA accommodates SATVOICE through arrangements with the recognized Aeronautical Mobile Satellite (Route) Service (AMS(R)S) providers. Direct SATVOICE contact between the pilot and ATC is currently limited to distress and urgency situations, or other exceptional circumstances only.

For oceanic communications service provider relay to ATC, SATVOICE short codes are published in the U.S. Aeronautical Information Publication (AIP). As this technology evolves, ensure that you comply with the latest authorizations. For additional guidance, refer to ICAO Document 10038, the Satellite Voice Operations Manual (SVOM).

4.3.4 Radio Frequency Changes. Radio frequencies are constantly changing. Thus, it is important that you consult the appropriate AIP, current oceanic charts, and commercial en route publications for the most current information.

• The North Atlantic Operations and Airspace Manual (ICAO NAT Document 007) describes North Atlantic (NAT) operations, to include communication and navigation procedures in NAT airspace.

• Commercially published navigation charts contain details of communication procedures on inserted panels. Exercise some caution in using this reference, as they may be on a different update cycle than the source documents and therefore could be not completely up to date.

4.4 CPDLC and Automatic Dependent Surveillance-Contract (ADS-C). Since the mid-1990s, data link communications systems have enhanced contact between ATS providers and the flight deck. These communication systems are now widely used throughout the world and have also led to the implementation of Automatic Dependent Surveillance (ADS) systems that further improve ATS capability. CPDLC technology improves communications between aircraft and ATS providers. CPDLC eliminates the often challenging HF voice communications that were the only communication link with oceanic and remote continental airspace air traffic controllers for decades. With CPDLC, you and the controller transfer ATC clearance requests and instructions digitally, reducing the likelihood of miscommunication. ADS-C is also widely used in oceanic and remote continental airspace and, in combination with CPDLC, has become required equipment to be assigned the most efficient routes across the NAT organized track system (OTS), where ATC allows minimum separation between aircraft.

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Note 1: In ADS-C, C = “Contract.” The controller sets up one or more electronic contracts with your aircraft to automatically provide time-triggered (periodic) and/or condition-triggered (e.g., deviation event) reports.

Note 2: Equipage with CPDLC does not eliminate the requirement for operable two-way radios. For most oceanic operations this means operable HF radios are required.

4.4.1 Access to Preferred Airspace. Since equipment like CPDLC and ADS-C improves the efficiency with which aircraft in oceanic and remote continental airspace can be controlled, such better-equipped aircraft are being better served through initiatives to reserve preferred blocks of oceanic airspace for those aircraft. Preferred altitudes and routes around the world are more readily issued to aircraft equipped with robust communications, navigation and surveillance capabilities.

4.4.2 Flight Management Computer Waypoint Reporting (FMC WPR) Service. FMC WPR service is one of the original data link capabilities, whereby your flight management computer (FMC) sends a waypoint report to the ATS provider via Aircraft Communications Addressing and Reporting System (ACARS) or CPDLC. It is gradually being replaced by automatic position reporting via ADS-C systems.

4.5 Data Link Systems—Operational Authorization to Use. We will grant operational authorization for operators to use data link by issuing OpSpec/MSpec/LOA A056, Data Link Communications, as appropriate.

Note: OpSpec/MSpec/LOA A056 also applies to datalink communications in overland areas, such as Aeronautical Telecommunication Network Baseline 1 (ATN B1) (formerly Link 2000+), used in European airspace.

4.5.1 Procedures for Obtaining Authorization. You are required to obtain operational authorization prior to using data link systems on designated oceanic and remote continental airspace routes. You can find our guidance on the process and procedures for operational authorization and aircraft data link system approval in the current editions of the following documents:

• AC 20-140, Guidelines for Design Approval of Aircraft Data Link Communication Systems Supporting Air Traffic Services (ATS).

• AC 120-70, Operational Authorization Process for Use of Data Link Communication System. Operators should consult geographic-specific areas of this document.

4.5.2 Data Link Requirements and Standards. You can consult ICAO Document 10037, GOLD, for additional information on data link requirements and standards.

4.6 ATC in Oceanic and Remote Continental Airspace.

4.6.1 Procedural Airspace. Oceanic and remote continental airspace is nonradar (i.e., where the separation of aircraft does not depend on ground-based radar coverage) and where there 4-6

is no other form of surveillance such as ADS-B. It is considered “procedural airspace.”

ATS providers in oceanic and remote continental airspace primarily provide procedural control and procedural separation to all flights.

4.6.1.1 These facilities issue clearances and instructions providing separation vertically and horizontally, based on the specific aircraft equipment authorizations you indicate on your flight plan. Because of ATC’s lower confidence in the aircraft’s reported position, adjacent aircraft under procedural control are kept farther apart from each other than under radar control.

4.6.1.2 ATC monitors your compliance with the issued clearance. Your aircraft position reports are processed for conformance with the clearance. If your aircraft is equipped with ADS-C, it provides trigger alerting for lateral and vertical deviations.

4.6.1.3 In order to make this nonradar airspace traffic management system work the way it is designed, you must provide timely and accurate time estimates (estimated time of arrival (ETA)) and operate with strict discipline and adherence to ATC clearances and procedures, both normal and contingency.

4.6.1.4 Controllers manage longitudinal separation in procedural airspace by assigning speeds, either true Mach number or true airspeed. An airspeed assignment is one element of an oceanic clearance. Proper separation of aircraft is dependent upon pilots maintaining the speed assigned with the oceanic clearance (not to be confused with the flight plan speed); therefore, compliance with the speed assignment is mandatory.

4.6.2 ICAO Procedures for Specific Geographical Areas. You will find detailed ICAO procedures for specific geographical areas in ICAO Document 7030, Regional Supplementary Procedures. FAA ATC bases its procedures for oceanic and remote continental airspace on ICAO Standards and Recommended Practices (SARP).

4.6.3 U.S. ATS in Oceanic and Remote Continental Airspace. The United States provides ATS in oceanic and remote continental airspace as follows:

• Atlantic Ocean: New York, Miami, and San Juan Flight Information Regions (FIR).

• Gulf of Mexico: Miami and Houston FIRs.

• Pacific Ocean: Oakland and Anchorage FIRs.

• Arctic Ocean: Anchorage Arctic FIR.

• Alaska Remote Continental Airspace: Anchorage Air Route Traffic Control Center (ARTCC).

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4.6.4 Advanced Technologies and Oceanic Procedures (ATOP). U.S. controllers utilize the ATOP (also referred to as Ocean21) System in the airspace of Oakland Oceanic, New York Oceanic, and Anchorage Oceanic FIRs.

4.6.4.1 Within this airspace, ATOP identifies suitably equipped aircraft for the controller (such as CPDLC and ADS-C), provides decision support tools for establishing the separation minima for all pairs of aircraft along a cleared profile, and provides aircraft profile conformance monitoring and protection.

4.6.4.2 ATOP deciphers flight plan information to determine which separation standards may be applied to a particular aircraft based on filed aircraft equipage. The system is capable of determining separation standards which may be applied between aircraft with different equipage and speeds. You must notify ATC immediately if your communications, navigation, and surveillance equipment capability degrades below that which you listed in your flight plan.

4.6.4.3 ATOP protects random routes of an individual aircraft and can issue conflict warnings in excess of 2 hours ahead of the event, depending on local adaptation. ATOP can also adapt to the separation standards applied by adjacent ATC facilities and can warn the controller when a conflict will occur based on the adjacent ATC facility’s requirements. This allows controllers to effectively plan for transitions to adjacent FIRs.

4.6.4.4 You can find specific information regarding ATC separation standards in the current edition of FAA Order JO 7110.65, Air Traffic Control. Additionally, trial periods where new separation standards are being applied will be announced via FAA International Notices to Airmen (NOTAM).

4.7 Special Use Airspace (SUA).

4.7.1 Warning Area. A warning area is airspace of defined dimensions extending from 3 NM outward from the coast of the United States that contains activity that may be hazardous to nonparticipating aircraft. The purpose of such a warning area is to warn nonparticipating pilots of the potential danger. A warning area may be located over domestic or international waters or both.

4.7.2 Prohibited Areas. ICAO specifies that these areas exist “above the land areas or territorial waters of a State, within which the flight of aircraft is prohibited.”

4.7.3 Restricted Areas. ICAO specifies that these areas exist “above the land areas or territorial waters of a State, within which the flight of aircraft is restricted in accordance with certain specified conditions.”

Note: Carefully review charts for these types of areas when you plan your flight, taking note of the area operating times and restrictions. You should also review applicable oceanic NOTAMs.

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4.8 Air Defense Identification Zones (ADIZ). Title 14 CFR part 99, Security Control of Air Traffic, discusses defense areas and ADIZ. You can check part 99, the latest U.S. AIP, the latest AIM (Chapter 5, Section 6), and all FAA NOTAMs Domestic/International to ensure compliance with national security requirements in the ADIZ.

4.9 World Geodetic System 1984 (WGS 84). ICAO and the United States endorse the WGS 84 or equivalent as the geodetic reference datum standard for air navigation latitude and longitude coordinates. WGS 84 was developed in response to the aviation community’s need for a common geodetic reference system and to standardize aeronautical surveys and related products. You should determine in advance whether any countries you intend to fly over or into are WGS 84-compliant. Information about WGS 84 compliance is often noted on plates used in terminal operations or on airfield diagrams. A State’s AIP generally notes compliance with WGS 84. Most areas of the world are listed as: 1) Unknown (U); 2) Partially Compliant (PC); 3) Compliant (C);

or 4) Noncompliant (NC) with WGS 84.

Note: Commercial charting vendors also post information on their Web sites about specific countries and their compliance with WGS 84.

4.9.1 Operations in Areas that Are Not WGS 84-Compliant. Flight manuals often include a note for long-range navigation systems (LRNS) indicating that, for countries or terminal areas that are not WGS 84-compliant, the crew should deselect the use of Global Navigation Satellite Systems (GNSS). You should be familiar with your flight manual limitations when flying in countries or terminal areas that are not WGS 84-compliant.

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CHAPTER 5. FLIGHT PLANNING GUIDANCE FOR INTERNATIONAL AND

OCEANIC AND REMOTE CONTINENTAL AIRSPACE OPERATIONS

5.1 Lead Time Requirements.

5.1.1 Preparation. Your preparation for a successful international flight, whether you fly large or small aircraft, starts with adequate planning and training. The lead time required for planning varies depending on such things as experience, training, and currency, as well as specific country requirements, and could exceed 30 days. Dispatch/flight locator departments available to 14 CFR part 121 operators and large 14 CFR part 135 operators could reduce certain planning time requirements.

5.1.1.1 Remember that many countries have long lead times to process visas or other necessary paperwork to approve an international flight. Depending upon the country, it may take up to 6 weeks to obtain visas and/or overflight and landing permits.

5.1.1.2 Ensure you are aware of current and special notices relating to entry and overflight requirements for the countries on your itinerary. In most cases outside North America and Europe, you obtain prior permission to land in or overfly a country directly from that country’s Civil Aviation Authority (CAA). You can also find information on immunizations, ports of entry, and other important requirements in the country’s Aeronautical Information Publication (AIP) and in various commercial publications.

5.1.2 Verification. You need to allow enough lead time to ensure your planning is thorough, complete, and correct. Always cross-check and verify any flight planning products against the appropriate source documents. By doing so, you could uncover potential errors before they result in a pilot deviation.

5.2 Preparing an Itinerary.

5.2.1 Itinerary Factors. Preparing the itinerary is one of the most important aspects of your international flight. You may want to consider the following questions when developing your itinerary:

1. To which destinations do I intend to fly (or overfly)?

2. Via what routes and altitudes?

3. Are there any terrain clearance concerns along those routes at those altitudes?

4. Have I identified any concerns with suitable equal time point (ETP) alternates along those routes and altitudes?

5. Are there any pitfalls I should be aware of from each State’s AIP?

6. What communications, navigation, and surveillance equipment and authorizations must I have in order to fly my intended routes and altitudes?

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7. Will I be operating in Special Area of Operation (SAO)? Do I have the necessary operational authorization(s) to do so?

8. With regard to my Global Navigation Satellite System (GNSS) equipment, are there any WGS 84 compliance issues in countries I intend to transit?

(Paragraph 4.9 provides information on WGS 84.)

9. What survival equipment must I have on board in order to fly my intended routes?

10. Are there suitable en route and destination alternates available in the event of an emergency diversion at other than my intended en route altitude?

Are there terrain clearance or oxygen considerations at those divert altitudes?

11. Does my preferred destination have instrument approaches and arrival and departure procedures that are compatible with my aircraft equipment and authorizations?

12. What crew rest requirements will I have for each destination?

Note: See paragraph 5.3 below regarding fatigue management issues.

13. Do I intend to use a flight planning or dispatch service for my trip?

14. If my routes take me through oceanic airspace, have I reviewed the following:

• Oceanic error mitigation procedures?

• Oceanic flight planning, plotting charts, navigation, and waypoint procedures?

• My oceanic checklist?

• Strategic Lateral Offset Procedure (SLOP) procedures?

• En route procedures for each airspace I will pass through?

• Oceanic contingency procedures?

15. Are there specific pilot certification, type rating, and/or medical certificate requirements for the countries I’ll be visiting? Are single-pilot operations authorized?

16. Will my intended route take me through areas of volcanic activity?

17. If my route takes me through polar areas, have I researched the unique risks inherent to operations on polar routes?

5.2.2 Country-Specific Issues and Requirements. As part of your itinerary preparation, asking the following additional questions can help you determine the country-specific issues/airspace requirements that might affect your international flight:

1. Do I require overflight and landing permits for any of the airspace/airfields I will transit?

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2. How much will overflight and landing fees cost, and how do I pay for each airspace and destination I intend to transit (e.g., credit card, cash, local currency, U.S. currency)?

3. How much advance notification do I need to provide prior to arrival?

Note: All countries require some form of advance notification of arrival.

You should carry a copy of the advance notification, as well as confirmation that the notification was sent. This is particularly important for countries that do not normally return approvals.

4. What are the availability, types, and duration of visas, tourist cards, and other required entry documents for all countries I intend to visit, as well as those with potential alternate airports (in the event I have to divert)?

Note: Some countries require that you have a visa for the next country of entry before departure, as well as proof of required immunizations for that country.

You can obtain this information from the U.S. Department of State (DOS).

5. Are there prohibitions, restrictions, and/or applicable notices for countries I intend to visit?

Note: The FAA’s Web site includes a special section on prohibitions, restrictions, and notices applicable to foreign countries at http://www.faa.gov/air_traffic/publications/us_restrictions/. You should pay particularly close attention to this aspect of your flight planning.

6. What is the normal work week for countries I intend to overfly/enter?

Note: Understanding this will help you coordinate for visas and overflight/landing permits. You can obtain this information from the DOS.

7. Are there any import regulations I need to consider, given the amount of time I intend to remain in the countries on my route?

Note: Aircraft that remain within the territorial limits of a country for an extended period of time may become subject to import regulations and impoundment.

Determine in advance the number of days that an aircraft may remain in any country where the aircraft will land.

8. What hours are customs, immigration, and other services operational?

9. Do I intend to conduct any operations that might be considered “cabotage?”

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5.2.3 Airport-Specific Issues. Consider the following airport-specific issues when planning for your overseas trip:

1. What time considerations can affect your trip?

• What is local time at each of my destination airports in terms of Coordinated Universal Time (UTC)?

• What is local time at my original departure airport?

• Are there restrictions on operating at night in the countries I intend to transit?

• Do any of the airspaces/destinations I intend to transit require slot times?

2. Is a Prior Permission Only (PPO) number required for landing?

3. Do my preferred destination and alternate airfields have the appropriate grade of fuel and other types of aircraft handling services available?

4. Are maintenance services available at my destination airfields?

5. Should I bring spare parts for my aircraft?

6. Will I have lodging available at the destination?

5.3 Crew Fatigue.

5.3.1 Fatigue Management. International travel typically involves crossing time zones and interrupting normal sleep patterns (circadian rhythm). Ensure you have a plan for how you will manage fatigue for you and your crew.

5.3.2 Fatigue Management Strategies. The current edition of AC 120-100, Basics of Aviation Fatigue, discusses strategies to mitigate the effects of fatigue and is an excellent resource.

The current edition of AC 120-103, Fatigue Risk Management Systems for Aviation Safety, discusses the Fatigue Risk Management Systems (FRMS) prescribed in 14 CFR part 117. While part 117 does not apply to all operators, we recommend you review both ACs as the contents cover issues that are important to all aircrews.

5.3.3 Self-Care and Time Zone Differences. Having a high level of physical fitness, using caffeine strategically, and avoiding alcohol can help you adjust to time zone differences, allow your body to rest better, and help make you a more effective, safer operator.

5.3.4 Preparing to Mitigate Fatigue. Inquire in advance about day sleeping or noise levels in the location where you intend to get your crew rest. This will help your crewmembers know what challenges to good rest might lie ahead. You should also consider adding one or more pilots beyond that for which the aircraft is certified for long-duration flights or those outside of normal sleep times. This will help mitigate fatigue issues and promote safer flying.

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