ADIRU failure once again?
In 2005, a Malaysian Airlines B777-200 (9M-MRG) was on a flight from Perth to Kuala Lumpur when it experienced a failure of its navigation system. The airplane suddenly climbed to FL410, then dropped 4000 feet, then climbed 2000 feet. The pilots flew the airplane manually back to Perth. Australian authorities investigated the incident. They determined that the failure was in the "operating software of the air data inertial reference unit (ADIRU), a device that supplies acceleration figures to the aircraft's flight computer." The device was manufactured by Honeywell and contained the fourth version of the operating system. A review of the software showed that the error did exist on the first three versions of the software, but had been suppressed by other features of the software. These other features were removed during the transition from the third version to the fourth version.
The problem was serious enough for the FAA to issue an emergency airworthiness directive in August 2005 to all B777 operators to revert to version three of the operating system.
Note that the airplane lost on March 8, 2014, was 9M-MRO, apparently a sister ship.