India, Sept. 5 -- At 9.32 am on August 4, the passengers on Air India flight AI2379 were two hours into a routine journey from Phuket to Delhi. The aircraft was cruising at 36,000 feet and the seat belt signs were off.

Then the aircraft climbed 372 feet above its assigned altitude and fell 292 feet below it. Twenty-four of the 145 people on board were hurt, four of them seriously. The Aircraft Accident Investigation Bureau's damage inventory records cracked ceiling panels across at least a dozen rows, two overhead bin doors dislodged from their hinges, broken handrails, a broken emergency exit handle, a bent crew seat and a lavatory commode uprooted from its mounting.

A 664-foot change in height is not unusual. An aircraft descending lo...