On May 19, 2016 at 9:09 p.m. local time (23:09 UMT)[1] EgyptAir Flight MS 804, an Airbus A320, departed Paris bound for Cairo carrying 56 passengers and 10 crew. Its scheduled arrival time was 01:15 UMT. At 23:24 UMT the aircraft entered Greek airspace. Air traffic controllers last spoke with the pilot, who reported no problems, at 23:48 UMT. At 00:26 UMT data reported by the ACARS (Aircraft Communications Addressing and Reporting System) satellite communications system indicated smoke in the forward lavatory. One minute later, at 00:27 UMT, ACARS reported smoke in the avionics bay below the cockpit and a fault in the right side cockpit window. At the same time air traffic controllers attempted to contact the aircraft, but despite repeated efforts no response was received. The aircraft disappeared from radar at 00:29.

Radar returns indicated that the aircraft first deviated 90 degrees to the left of its flightpath, then made a full 360 degree circle to the right, while descending from 38,000 feet to 10,000 feet of altitude before disappearing at 00:30 UMT, approximately 175 miles north of the Egyptian Mediterranean coast.

An intensive search effort soon located debris floating on the ocean surface, and wreckage was found on the sea floor at a depth of nearly 10,000 feet. “Pings” from the cockpit voice recorder (CVR) were detected, and on June 16 the damaged CVR was located and recovered. The following day the flight data recorder (FDR) was also recovered. The recorders’ memory chips were badly damaged, and were flown to the Paris where the French accident investigation bureau cleaned and repaired them. They were then returned to Egypt for analysis. The U.S. National Transportation Safety Board is participating in the investigation by Egyptian civil aviation authorities, and the Paris prosecutor’s office has opened an investigation into the circumstances of the accident.

What is Known at This Point?

In the immediate aftermath of the accident Egypt’s civil aviation minister said that terrorism was a more likely explanation than equipment failure or some other catastrophic event, and the head of Russia’s Federal Security Service (FSB) was also quoted as saying, “In all likelihood, this is a terrorist act.” But no group took credit for the event, and the Paris prosecutor said that no evidence has been found to link the crash to terrorism.

The Egyptian authorities have stated that the FDR data confirms smoke in the forward lavatory and the equipment bay, and that wreckage from the forward area of the aircraft showed signs of high temperature damage and soot. In July they stated that fire was mentioned on the CVR recording, and that the aircraft most likely broke up in midair after a fire that quickly overwhelmed the crew, but that they could not determine whether the fire was caused by a mechanical malfunction or a malicious act.

An in-flight fire is among the most hazardous situations flight crew can encounter, and can quickly lead to catastrophic loss of the aircraft. Once a fire has become established, it is unlikely that the crew will be able to extinguish it. It is a pilot’s nightmare.

In-flight fires involving air transport aircraft have been relatively rare in recent years. The best known incident is Swissair Flight 111, a McDonnell Douglas MD-111 en route from New York to Geneva on September 2, 1998. One hour after takeoff a fire broke out in the overhead area above the cabin ceiling in the forward part of the aircraft. The crew attempted to make an emergency landing at Halifax, Nova Scotia, but fire spread rapidly, making it impossible to control the aircraft, which plunged into the sea five miles from the coast of Nova Scotia. The Canadian Transportation Safety Board, which investigated the accident, was unable to determine the cause of the fire.

While there is little doubt that EgyptAir Flight 804 was also brought down by fire, it remains to be seen whether the cause of the fire can be determined. The Egyptian authorities have released no information since July, and have not indicated when an interim report or further investigation results will be released.