# NTSB investigations: Enroute

NTSB aviation accident and incident investigations since 1962: the probable cause, findings, aircraft, crew, weather and docket of each, linked to the FAA registry and the FAA’s own reports.

Page 279 of 718 · 35,885 cases

## Cases, newest first

- [NTSB MIA90LA058](https://openairdocs.org/ntsb/MIA90LA058.md): Mcdonnell Douglas DC-10-10 · San Juan, PR · Accident · Serious injuries · Limited investigation · Final report · Jan 20, 1990 · N124AA · No damage
  > Inadvertent flight of the airplane into an area of turbulence associated with a developing rain storm.
- [NTSB NYC90LA053](https://openairdocs.org/ntsb/NYC90LA053.md): Mooney M20 · Brogue, PA · Accident · Minor injuries · Limited investigation · Final report · Jan 19, 1990 · N231FH · Destroyed
  > Off airport landing due to an engine power loss due to failure of the no. 2 crankshaft bearing.
- [NTSB NYC90LA052](https://openairdocs.org/ntsb/NYC90LA052.md): Cessna C150 · E. Prospect, PA · Accident · Serious injuries · Limited investigation · Final report · Jan 19, 1990 · N6017G · Destroyed
  > Pilot's improper execution of emergency procedures after the engine failed. The pilot lost control of the airplane while maneuver the airplane back to the airstrip during the forced landing. The pilot stalled the airplane at too low an altitude to recover.
- [NTSB ATL90MA051](https://openairdocs.org/ntsb/ATL90MA051.md): Learjet 23 · Ansonia, OH · Accident · 2 fatal · Major investigation · Final report · Jan 18, 1990 · N331DP · Destroyed
  > The flight crew became incapacitated for undetermined reasons and lost control of the airplane.
- [NTSB DEN90FA043](https://openairdocs.org/ntsb/DEN90FA043.md): Cessna 208A · Leadville, CO · Accident · 1 fatal · Field investigation · Final report · Jan 17, 1990 · N835FE · Destroyed
  > Diversion of the pilot's attention, resulting in an in flight collision with terrain during normal cruise flight.
- [NTSB MKC90FA044](https://openairdocs.org/ntsb/MKC90FA044.md): Cessna P210N · Newton, KS · Accident · Serious injuries · Field investigation · Final report · Jan 16, 1990 · N4589K · Substantial damage
  > Loss of engine power for an undetermined reason. Darkness and the resultant delay in flaring to land were related factors.
- [NTSB LAX90LA271](https://openairdocs.org/ntsb/LAX90LA271.md): Cessna R172K · Lone Pine, CA · Accident · 1 fatal · Limited investigation · Final report · Jan 14, 1990 · N758UV · Destroyed
  > The pilot's decision to continue VFR flight into instrument meteorological conditions. Factors to the accident were the adverse weather conditions, mountainous terrain, and the likely effect of hypoxia on the pilot.
- [NTSB FTW90LA055](https://openairdocs.org/ntsb/FTW90LA055.md): Piper PA-32R-301T · Liberty, TX · Accident · No injuries · Limited investigation · Final report · Jan 14, 1990 · N8128B · Substantial damage
  > Loss of engine power due to failure of the tappet faces. A factor in the accident was the unsuitable terrain in which the forced landing was made.
- [NTSB MKC90LA046](https://openairdocs.org/ntsb/MKC90LA046.md): Cessna 150 · York, MN · Accident · No injuries · Limited investigation · Final report · Jan 13, 1990 · N152HB · Substantial damage
  > Powerplant failure due to undetermined causes.
- [NTSB MIA90LA052](https://openairdocs.org/ntsb/MIA90LA052.md): Cessna 210M · Ocala, FL · Accident · No injuries · Limited investigation · Final report · Jan 12, 1990 · N9064M · Substantial damage
  > Separation of the throttle plate, due to improper securing of the attach screws during an overhaul.
- [NTSB FTW90FA051](https://openairdocs.org/ntsb/FTW90FA051.md): Bell UH-1B · San Diego, TX · Accident · 1 fatal · Field investigation · Final report · Jan 12, 1990 · N15SX · Destroyed
  > The pilot intentionally flew into instrument meteorological conditions during night VFR flight, and the helicopter subsequently collided with terrain.
- [NTSB NYC90LA049](https://openairdocs.org/ntsb/NYC90LA049.md): Piper PA-34-200T · Messena, NY · Accident · No injuries · Limited investigation · Final report · Jan 11, 1990 · N1506X · Substantial damage
  > The airplane striking a light pole during an off airport landing on a road, due to a double power loss for unknown reasons. Factors related to the accident were: the pilots unfamiliarity with the airplane.
- [NTSB ATL90LA050](https://openairdocs.org/ntsb/ATL90LA050.md): Piper PA-28-140 · Lithia Springs, GA · Accident · No injuries · Limited investigation · Final report · Jan 11, 1990 · N55862 · Substantial damage
  > Improper planning/decision by the pilot, which resulted in fuel exhaustion, due to an inadequate supply of fuel.
- [NTSB MIA90LA051](https://openairdocs.org/ntsb/MIA90LA051.md): Mitsubishi MU-2B-25 · Jacksonville, FL · Accident · No injuries · Limited investigation · Final report · Jan 9, 1990 · N666HB · Substantial damage
  > Failure of the owner/operator to obtain proper maintenance and inspection of the aircraft. Factors related to the accident were: operation of the aircraft by the pilot without a current annual inspection (known deficiency), an oil leak in the left engine…
- [NTSB ATL90LA049](https://openairdocs.org/ntsb/ATL90LA049.md): Cessna 150L · Talladega, AL · Accident · Serious injuries · Limited investigation · Final report · Jan 8, 1990 · N7950F · Destroyed
  > The pilot's improper inflight decision to attempt to continue VFR flight IMC conditions with no instrument rating, clearance or experience.
- [NTSB ATL90LA048](https://openairdocs.org/ntsb/ATL90LA048.md): Cessna 172B · Killen, AL · Accident · No injuries · Limited investigation · Final report · Jan 7, 1990 · N7401X · Substantial damage
  > Inadequate pre-flight planning by the pilot in command which resulted in fuel exhaustion during cruise flight.
- [NTSB MIA90LA048](https://openairdocs.org/ntsb/MIA90LA048.md): Cessna 172RG · Astatula, FL · Accident · No injuries · Limited investigation · Final report · Jan 5, 1990 · N6290R · Substantial damage
  > Loss of engine power for an undetermined reason during a simulated forced landing.
- [NTSB MIA90IA047](https://openairdocs.org/ntsb/MIA90IA047.md): Boeing 727-251 · Madison, FL · Incident · No injuries · Incident investigation · Final report · Jan 4, 1990 · N2280 · Minor damage
  > The failure of company service personnel to properly service the airplane forward lavatory.
- [NTSB FTW90LA049](https://openairdocs.org/ntsb/FTW90LA049.md): Cessna 172E · Hammond, LA · Accident · Minor injuries · Limited investigation · Final report · Jan 4, 1990 · N3531S · Destroyed
  > Pilot in command's initiation and continuation of the flight into an area of known IMC weather conditions and his subsequent inability to land prior to running out of fuel. Contributing factors to the accident were the pilot's failure to exercise good…
- [NTSB NYC90LA045](https://openairdocs.org/ntsb/NYC90LA045.md): Aeronca 11CC · Slippery Rock, PA · Accident · No injuries · Limited investigation · Final report · Jan 3, 1990 · N4636E · Substantial damage
  > Loss of airspeed and an inadvertent stall by the pilot during an attempted return to the airport, following a power loss due to carburetor ice.
- [NTSB BFO90FA017](https://openairdocs.org/ntsb/BFO90FA017.md): Douglas DC-10 · Baltimore, MD · Accident · Serious injuries · Field investigation · Final report · Jan 2, 1990 · N109AA · No damage
  > Injuries associated with the evacuation of the aircraft.
- [NTSB LAX90FA061](https://openairdocs.org/ntsb/LAX90FA061.md): Boeing 737-204 · Tucson, AZ · Accident · Minor injuries · Field investigation · Final report · Dec 31, 1989 · N198AW · Substantial damage
  > Failure of the operator's maintenance personnel to detect an electrical wire which had chafed against a hydraulic line and which eventually arced causing a leak in the hydraulic line and subsequent fire and hydraulic system failure. In addition, previous wear…
- [NTSB MIA90FA046](https://openairdocs.org/ntsb/MIA90FA046.md): Cessna 172N · Meridian, MS · Accident · 1 fatal · Field investigation · Final report · Dec 29, 1989 · N733FK · Destroyed
  > In flight loss of control by the pilot while flying in instrument meteorological conditions. Contributing factor(s) was: the pilot's apprehension toward instrument flying and the adverse weather conditions that existed at the time.
- [NTSB DEN90LA037](https://openairdocs.org/ntsb/DEN90LA037.md): Beech 35 · Tularosa, NM · Accident · Serious injuries · Limited investigation · Final report · Dec 29, 1989 · N9K · Substantial damage
  > The pilot's VFR flight into instrument meteorological conditions (IMC), and his failure to see and avoid the road sign during the precautionary landing. The adverse weather was a realted factor.
- [NTSB ATL90LA047](https://openairdocs.org/ntsb/ATL90LA047.md): Morrisey 2150A · Winston Salem, NC · Accident · Serious injuries · Limited investigation · Final report · Dec 29, 1989 · N5145V · Substantial damage
  > A blocked fuel vent line, which prevented normal fuel flow to the engine and subsequent loss of power.
- [NTSB CHI90FA055](https://openairdocs.org/ntsb/CHI90FA055.md): Beech A24R · Merrill, WI · Accident · 3 fatal · Field investigation · Final report · Dec 28, 1989 · N37329 · Destroyed
  > Flight into known adverse weather by the pilot, and structural/wing ice. Factors related to the accident were: the icing conditions and trees in the area of the accident.
- [NTSB MIA90LA042](https://openairdocs.org/ntsb/MIA90LA042.md): Boeing 727-225B · Miami, FL · Accident · 1 fatal · Limited investigation · Final report · Dec 27, 1989 · N822EA · No damage
  > Fatal injury to a stowaway due to asphyxia and hypothermia.
- [NTSB LAX90LA057](https://openairdocs.org/ntsb/LAX90LA057.md): Beech 33 · Gorman, CA · Accident · Minor injuries · Limited investigation · Final report · Dec 27, 1989 · N875R · Substantial damage
  > The malfunctioning propeller governor, and the pilot's misjudgement of altitude and distance of the approach path during an emergency landing. Factors contributing to the accident were: the power lines across the approach path to the runway and the…
- [NTSB CHI90LA054](https://openairdocs.org/ntsb/CHI90LA054.md): Beech V35B · North Canton, OH · Accident · No injuries · Limited investigation · Final report · Dec 27, 1989 · N2105L · Substantial damage
  > Continued flight by the pilot into known adverse weather conditions, and his delay in diverting to an alternate airport, which resulted in accumulation of airframe icing. Factors related to the accident were: the adverse weather and runway/terrain conditions.
- [NTSB NYC90FA041](https://openairdocs.org/ntsb/NYC90FA041.md): Cessna 172N · Washington Twp, NJ · Accident · 3 fatal · Field investigation · Final report · Dec 26, 1989 · N3353E · Destroyed
  > The failure of the pilot to properly pre-flight plan and execute the VFR flight. Factor's related to the accident were: the pilot's inexperience; no visual cues (lights) due to dark night conditions; the pilot's disregard of the weather briefing.
- [NTSB CHI90LA047](https://openairdocs.org/ntsb/CHI90LA047.md): Cessna 210 · New Phila, OH · Accident · No injuries · Limited investigation · Final report · Dec 26, 1989 · N59145 · Substantial damage
  > The pilot's failure to drain all of the trapped water from the fuel system prior to flight. Factors related to the accident were: the unfavorable wind condition and trees in the emergency landing area.
- [NTSB MIA90LA040](https://openairdocs.org/ntsb/MIA90LA040.md): Mooney M20 · Fort Lauderdale, FL · Accident · No injuries · Limited investigation · Final report · Dec 24, 1989 · N6879N · Destroyed
  > Partial loss of engine power for an unknown reason.
- [NTSB SEA90FA027](https://openairdocs.org/ntsb/SEA90FA027.md): Cessna 172N · Nordland, WA · Accident · 2 fatal · Field investigation · Final report · Dec 21, 1989 · N2228E · Destroyed
  > Undetermined.
- [NTSB NYC90FA040](https://openairdocs.org/ntsb/NYC90FA040.md): Piper PA-60-602P · Frenchtown, NJ · Accident · 1 fatal · Field investigation · Final report · Dec 21, 1989 · N6894Y · Destroyed
  > The inadequate maintenance and inspection of the turbocharger tailpipe exhaust stack on the right engine by the mechanic(s). The failure of the tailpipe permitted heat from the exhaust to weaken the main spar of the right wing resulting in a catastrophic…
- [NTSB CHI90LA048](https://openairdocs.org/ntsb/CHI90LA048.md): Cessna 310Q · Grand Rapids, MI · Accident · No injuries · Limited investigation · Final report · Dec 20, 1989 · N117CC · Substantial damage
  > The undetermined engine compartment fire during the initial climbout. A factor was the failure of the pilot to shut off the fuel supply to the engine.
- [NTSB LAX90LA054](https://openairdocs.org/ntsb/LAX90LA054.md): Piper PA-18-150 · Bumble Bee, AZ · Accident · No injuries · Limited investigation · Final report · Dec 19, 1989 · N4101E · Substantial damage
  > The failure of the student pilot to apply carburetor heat in a timely manner. Contributing to the accident were the carburetor icing conditions and the desert terrain.
- [NTSB CHI90LA046](https://openairdocs.org/ntsb/CHI90LA046.md): Cessna 150M · Lacrosse, WI · Accident · Minor injuries · Limited investigation · Final report · Dec 18, 1989 · N704NP · Substantial damage
  > The student pilot's improper pre-flight planning/preparation, which did not include a plan to refuel the aircraft as necessary. The student pilot's lack of total experience contributed to this accident, as did the cfi's inadequate supervision of the student.
- [NTSB ATL90LA041](https://openairdocs.org/ntsb/ATL90LA041.md): Beech A36 · Nashville, NC · Accident · No injuries · Limited investigation · Final report · Dec 17, 1989 · N8EM · Substantial damage
  > A loss of engine power for undetermined reasons. A factor related to the accident was the ditch the airplane contacted.
- [NTSB SEA90FA030](https://openairdocs.org/ntsb/SEA90FA030.md): Crawford-Gordon Thorp T-18 · Austin, NV · Accident · 1 fatal · Field investigation · Final report · Dec 16, 1989 · N111GC · Destroyed
  > An improper major alteration performed by the pilot. As a result of this modification, the propeller failed in flight.
- [NTSB NYC90FA039](https://openairdocs.org/ntsb/NYC90FA039.md): Piper PA-31-350 · Cairo Township, NY · Accident · 6 fatal · Field investigation · Final report · Dec 15, 1989 · N45CH · Destroyed
  > The pilot's decision to fly into the known adverse weather and his failure to select an altitude that would provide terrain clearance. Factors were: the adverse weather and the pilot's disregard for the forecasted conditions.
- [NTSB MIA90IA039](https://openairdocs.org/ntsb/MIA90IA039.md): Boeing 727 · Ormond Beach, FL · Incident · No injuries · Incident investigation · Final report · Dec 15, 1989 · N64339 · 2 aircraft · No damage
  > Failure of the pilot in command in the Beech 300 to comply with an ATC clearance in a timely manner, while diverting his attention, and failure of the ATC controller to assure that IFR separation was maintained.
- [NTSB ANC90FA020](https://openairdocs.org/ntsb/ANC90FA020.md): Boeing 747-400 · Anchorage, AK · Accident · No injuries · Field investigation · Final report · Dec 15, 1989 · PHBFC · Substantial damage
  > Inadvertent encounter with volcanic ash cloud, which resulted in damage from foreign material (foreign object) and subsequent compressor stalling of all engines. A factor related to the accident was: the lack of available information about the ash cloud to…
- [NTSB CHI90DEV01](https://openairdocs.org/ntsb/CHI90DEV01.md): Cessna 210D · Jerseyville, IL · Accident · Minor injuries · Final report · Dec 10, 1989 · N3955Y · Substantial damage
  > A total loss of engine power for an undetermined reason. A factor in the accident was the rough uneven terrain in the forced landing area.
- [NTSB NYC90FA038](https://openairdocs.org/ntsb/NYC90FA038.md): Boeing 727-31 · Newark, NJ · Accident · No injuries · Field investigation · Final report · Dec 9, 1989 · N727PJ · Substantial damage
  > Thermal distress of the first stage turbine blades of the nuber one engine causing a degradation of material properties which resulted in blade fractures. The reason for the thermal distress was not determined.
- [NTSB LAX90LA050](https://openairdocs.org/ntsb/LAX90LA050.md): Hughes 369HS · Waimea, HI · Accident · No injuries · Limited investigation · Final report · Dec 9, 1989 · N9161F · Substantial damage
  > The improper installation of the pc tube by company maintenance personnel, which resulted in fatigue failure of the tube due to induced bending stresses.
- [NTSB SEA90FA028](https://openairdocs.org/ntsb/SEA90FA028.md): Cessna 210-5 (205) · Rainier, WA · Accident · 2 fatal · Field investigation · Final report · Dec 8, 1989 · CFOXF · Destroyed
  > Continued flight by the pilot into known adverse weather conditions, and his failure to maintain sufficient altitude/clearance from wooded mountainous terrain. Factors related to the accident were: darkness and the weather/terrain conditions.
- [NTSB MIA90LA037](https://openairdocs.org/ntsb/MIA90LA037.md): Cessna 172 · Atlantic Ocean (Atlantic Ocean) · Accident · 1 fatal · Limited investigation · Final report · Dec 7, 1989 · N8785B · Destroyed
  > The engine seized from oil starvation (lack of oil or oil pressure), which resulted in the aircraft being ditched at sea.
- [NTSB LAX90LA049](https://openairdocs.org/ntsb/LAX90LA049.md): Cessna 150D · Inyokern, CA · Accident · No injuries · Limited investigation · Final report · Dec 6, 1989 · N4390U · Substantial damage
  > The pilot's failure to use carburetor heat when climatic conditions were conducive to the formation of carburetor ice.
- [NTSB ATL90LA037](https://openairdocs.org/ntsb/ATL90LA037.md): Beech A36 · Charlotte, NC · Accident · No injuries · Limited investigation · Final report · Dec 6, 1989 · N2997S · Substantial damage
  > The failure of the airplane engine due to fuel exhaustion over terrain unsuitable for the forced landing.
- [NTSB DEN90LA029](https://openairdocs.org/ntsb/DEN90LA029.md): Piper PA-28-161 · Grand Forks, ND · Accident · No injuries · Limited investigation · Final report · Dec 2, 1989 · N130ND · Substantial damage
  > Failure of the CFI to utilize carburetor heat prior to the induction icing and power loss. Contributing to the accident was the cfi's continued VFR flight into known and forecast instrument meteorological conditions.

Next page: https://openairdocs.org/ntsb-phases/400/cases.md?page=280

## The whole list in SQL

Runs in DuckDB 1.2 or later on the release's Parquet files over HTTPS:

```sql
WITH phase_names(main, name) AS (VALUES (100, 'Prior to flight'), (150, 'Standing'), (200, 'Pushback/towing'), (250, 'Taxi'), (300, 'Takeoff'), (350, 'Initial climb'), (400, 'Enroute'), (450, 'Maneuvering'), (500, 'Approach'), (550, 'Landing'), (600, 'Emergency descent'), (650, 'Uncontrolled descent'), (700, 'Post-impact'), (750, 'After landing'), (800, 'Other'), (990, 'Unknown')),
  crosswalk(code, main, name) AS (VALUES (500, 150, 'Standing'), (501, 150, 'Standing - pre-flight'), (502, 150, 'Standing - starting engine(s)'), (503, 150, 'Standing - engine(s) operating'), (504, 150, 'Standing - engine(s) not operating'), (505, 150, 'Standing - idling rotors'), (510, 250, 'Taxi'), (511, 200, 'Taxi - pushback/tow'), (512, 250, 'Taxi - to takeoff'), (513, 250, 'Taxi - from landing'), (514, 250, 'Taxi - aerial'), (520, 300, 'Takeoff'), (521, 300, 'Takeoff - roll/run'), (522, 350, 'Takeoff - initial climb'), (523, 300, 'Takeoff - aborted'), (530, 400, 'Climb'), (531, 400, 'Climb - to cruise'), (540, 400, 'Cruise'), (541, 400, 'Cruise - normal'), (542, 400, 'Maneuvering - holding (IFR)'), (550, 400, 'Descent'), (551, 400, 'Descent - normal'), (552, 600, 'Descent - emergency'), (553, 650, 'Descent - uncontrolled'), (560, 500, 'Approach'), (561, 500, 'Approach - VFR pattern - downwind'), (562, 500, 'Approach - VFR pattern - base turn'), (563, 500, 'Approach - VFR pattern - base leg/base to final'), (564, 500, 'Approach - VFR pattern - final approach'), (565, 500, 'Go-around (VFR)'), (566, 500, 'Approach - IAF to FAF/outer marker (IFR)'), (567, 500, 'Approach - FAF/outer marker to threshold (IFR)'), (568, 500, 'Circling (IFR)'), (569, 500, 'Missed approach (IFR)'), (570, 550, 'Landing'), (571, 550, 'Landing - flare/touchdown'), (572, 550, 'Landing - roll'), (573, 550, 'Landing - aborted'), (574, 550, 'Emergency landing'), (575, 550, 'Emergency landing after takeoff'), (576, 600, 'Emergency descent/landing'), (580, 450, 'Maneuvering'), (581, 450, 'Maneuvering - aerial application'), (582, 450, 'Maneuvering - turn to reverse direction'), (583, 450, 'Maneuvering - turn to landing area (emergency)'), (590, 450, 'Hover'), (591, 450, 'Hover - in ground effect'), (592, 450, 'Hover - out of ground effect'), (600, 800, 'Other'), (610, 990, 'Unknown')),
  current_codes AS (
    SELECT e.case_mkey, TRY_CAST(e."tier1Number" AS INTEGER) AS code,
      row_number() OVER (PARTITION BY e.case_mkey ORDER BY coalesce(e."isDefiningEvent", false) DESC, e.position) AS n
    FROM 'https://openairdocs.org/data/latest/ntsb_events.parquet' e
    WHERE e.aircrafts_position = 1 AND e."tier1Number" GLOB '[1-9][0-9]*'
      AND (e."isDefiningEvent" OR e.case_mkey IN (SELECT "mKey" FROM 'https://openairdocs.org/data/latest/ntsb_case_detail.parquet' WHERE "isPre1982"))
  ),
  phases AS (
    SELECT case_mkey, 'current' AS scheme, code, CASE WHEN code >= 990 THEN 990 ELSE code // 50 * 50 END AS main
    FROM current_codes WHERE n = 1
    UNION ALL
    SELECT o.case_mkey, 'older', o."phaseOfFlightCode", w.main
    FROM 'https://openairdocs.org/data/latest/ntsb_occurrences.parquet' o JOIN crosswalk w ON w.code = o."phaseOfFlightCode"
    WHERE o.aircrafts_position = 1 AND o."occurrenceNumber" = 1 AND o.case_mkey NOT IN (SELECT case_mkey FROM current_codes)
  ),
  case_phases AS (
    SELECT p.*, c."eventDate", c."highestInjuryLevel" = 'Fatal' AS fatal, a.aircraft_model_code
    FROM phases p JOIN 'https://openairdocs.org/data/latest/ntsb_case_detail.parquet' c ON c."mKey" = p.case_mkey
    LEFT JOIN 'https://openairdocs.org/data/latest/ntsb_aircrafts.parquet' a ON a.case_mkey = p.case_mkey AND a.position = 1
    WHERE c."eventDate" >= DATE '1962-01-01' AND p.main IN (SELECT main FROM phase_names)
  )
SELECT c."ntsbNumber", c."eventDate", c."eventType", c."eventCity", c."eventStateOrRegion", a.n_number, a."aircraftMake", a."aircraftModel", c."highestInjuryLevel", c."totalFatal", c."completionStatus", c.report_url
FROM 'https://openairdocs.org/data/latest/ntsb_case_detail.parquet' c LEFT JOIN 'https://openairdocs.org/data/latest/ntsb_aircrafts.parquet' a ON a.case_mkey = c."mKey" AND a.position = 1
WHERE c."mKey" IN (SELECT case_mkey FROM case_phases WHERE main = 400)
ORDER BY c."eventDate" DESC, c."ntsbNumber" DESC
```

This list as a web page: https://openairdocs.org/ntsb-phases/400/cases?page=279

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.