As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS NOT DECLARED DUE TO: BOTH FLIGHT DIRECTORS DROPPED OFF DURING TAKEOFF ROLL, FLIGHT DIRECTORS 2 RETURNED BUT NOT FLIGHT DIRECTORS 1. AIRCRAFT AIR INTERRUPTED BACK TO AND LANDED SAFELY AT JFK. TROUBLESHOT SYSTEM FOUND LEFT (ADIRU)-AIR DATA INERTIA REF UNIT AT FAULT REPLACED LEFT ADIRU. PER AMM 34-21-01. ACCOMPLISHED ALL REQUIRED CHECKS ALL CHECKS NORMAL.