Fire is the emergency that leaves the least time. On Swissair Flight 111, about 20 minutes passed between the first unusual smell in the cockpit and the aircraft hitting the sea, and Canada’s investigators found that even an immediate diversion could not have reached the runway in time. The fires that do the most harm are often hidden: in insulation above a ceiling, in a cargo hold, or as vapour inside a fuel tank.
Why fire is the emergency pilots fear most
Most emergencies give a crew time to work through a checklist. A spreading fire does not. Three things make it harder:
- It is often out of sight. The Transportation Safety Board of Canada (TSB) found that Swissair 111 had no smoke or fire detectors in the area above the cockpit ceiling where the fire started, and none were required.
- Smoke is hard to trace. Smoke and smell can come from air conditioning, galley ovens or electrics. The TSB found the Swissair 111 crew relied on sight and smell, which led them to take the first smoke for an air conditioning problem.
- The fire attacks the systems the crew needs. Wiring, displays and flight controls can fail one after another as the fire reaches them.
The accidents below are grouped on our fire or smoke page.
Swissair 111: smoke, wiring and insulation
On 2 September 1998, Swissair Flight 111, a McDonnell Douglas MD-11 registered HB-IWF, was flying from New York to Geneva with 215 passengers and 14 crew.
The flight. At 22:10:38 Atlantic Daylight Time, cruising at 33,000 feet, the pilots noticed an unusual odour, then briefly saw smoke near an air conditioning vent. At 22:14:15 they made an urgency call (pan-pan) and accepted a diversion to Halifax, 56 nautical miles ahead. Above the aircraft’s maximum landing weight, they planned to dump fuel and were turned out over the sea. Working through the smoke checklist, the captain switched off the cabin bus. Within seconds the autopilot disconnected and systems began to fail as the fire reached wiring above the cockpit. At 22:24:42 the crew declared an emergency. The flight recorders stopped at 22:25:41. At 22:31:18 the aircraft struck the water about 5 nautical miles south-west of Peggy’s Cove, Nova Scotia. All 229 people on board were killed.
What the TSB found. The TSB recovered about 98 per cent of the aircraft from the seabed and rebuilt the front of the fuselage. Its findings as to causes (report A98H0003) begin with certification standards. Those standards allowed materials that could be ignited and could sustain or spread a fire. The fire most likely started from a wire arcing event above the ceiling on the right side of the cockpit, near the rear wall. A wire in the in-flight entertainment network’s power supply cable showed arc damage in that area. The TSB said this arc was likely associated with the start of the fire, but it could not determine whether it was the first event. The metallised polyethylene terephthalate (MPET) film covering the insulation blankets was flammable. It was most likely the first material to ignite, and it made up most of what burned. The fire spread until it degraded the aircraft’s systems and the cockpit, and control was lost.
Could a faster landing have saved it? The TSB calculated that even a direct diversion at the first sign of smoke could not have put the aircraft on the runway before about 22:27. By then the fire had already disabled key systems. The aircraft type is on the McDonnell Douglas MD-11 page.
Swissair 551: a smoke-filled cockpit that ended safely
Five years earlier, another Swissair crew had a very different outcome. On 16 October 1993, Swissair Flight 551, a McDonnell Douglas MD-81 registered HB-INH, left Munich for Zurich with 88 passengers and 7 crew.
About ten minutes after take-off, smoke came from the overhead panel. The crew asked to return to Munich at once. Working through the electrical smoke checklist, they switched off the right generator, and almost all of the captain’s instruments failed as the smoke thickened. At 09:53 the captain handed control to the first officer. Smoke deposits made the charts unreadable, so the crew had to ask air traffic control for the landing system frequency. The aircraft landed on runway 08R at 09:58, 13 minutes after the request to return. Everyone got out. Fourteen passengers and one flight attendant were slightly hurt.
Germany’s Flugunfalluntersuchungsstelle (FUS) found a massive smouldering fire in the emergency power switch, which had failed through mechanical and electrical overload. It recommended a life limit of 10,000 operations for the switch on DC-9 series aircraft, and moving high-current switching out of the cockpit overhead panel. McDonnell Douglas set the limit by service bulletin, and the FAA made it mandatory. The crew’s early decision to turn back is the clearest contrast with Swissair 111. The report classed the event as an operational incident.
TWA 800: a centre fuel tank explosion
TWA Flight 800 was a Boeing 747-131, N93119, flying from New York to Paris on 17 July 1996 with 212 passengers and 18 crew. It was not a cabin fire. It was an explosion inside a fuel tank.
The 747 had arrived from Athens with its centre wing tank almost empty, holding only fuel the pumps could not reach. On the ground at JFK, the air conditioning packs, mounted directly beneath that tank, ran for hours on a warm day and heated the vapour inside. About 12 minutes after take-off, at 20:31:12 and about 13,800 feet, the fuel and air mixture in the centre tank exploded. The forward fuselage separated within seconds, and all 230 people on board were killed.
The NTSB (report AAR-00/03) found that the probable cause was the explosion of the centre wing fuel tank, from ignition of the flammable fuel and air mixture in the tank. It could not determine the ignition source with certainty. The most likely source was a short circuit outside the tank that let excessive voltage into it through wiring for the fuel quantity indication system. The FBI ran a criminal investigation alongside the NTSB’s and closed it without finding evidence of a criminal act. The theories about the crash, and the evidence on them, are covered in Plane Crashes With Disputed Causes. TWA 800 is one of the accidents in Boeing 747 Crashes, and the Boeing 747 page lists the others.
The NTSB rebuilt the aircraft from more than 95 per cent of the wreckage recovered from the sea. How Plane Crash Investigations Work explains how reconstructions like this are done.
Other in-flight fires
These events do not have pages on this site yet.
- Air Canada Flight 797, Cincinnati, 2 June 1983. Cabin crew on a DC-9 at 33,000 feet found smoke in the rear lavatory. The crew made an emergency descent and landed at Cincinnati, but 23 passengers could not get out and died in the fire. The NTSB found the probable causes were a fire of undetermined origin, an underestimate of how severe it was, and misleading information given to the captain about it. The time taken to decide to descend contributed to how severe the accident was.
- ValuJet Flight 592, the Everglades, 11 May 1996. A DC-9 crashed after a fire in its forward cargo hold, and all 110 people on board were killed. The NTSB found the fire began when chemical oxygen generators, carried improperly as cargo, were set off. Among the probable causes, it named the FAA’s failure to require smoke detection and fire suppression in that class of cargo hold (Class D).
- Saudia Flight 163, Riyadh, 1980. A Saudia Lockheed L-1011 TriStar was lost to a fire at Riyadh in 1980.
What changed
- Insulation that does not spread fire. In 2003 the FAA adopted new flammability tests for the thermal and acoustic insulation inside airliners. The rule said the old standards did not realistically cover how these materials can help a fire spread. The new tests cover flame spread in hidden areas and how well insulation keeps an outside fire from burning into the cabin after a crash. MPET-covered insulation was taken out of service.
- Land as soon as possible. After Swissair 111, an industry task force added “at any time” items to smoke and fire checklists. These tell crews to consider landing immediately whenever the situation becomes unmanageable, instead of finishing a diagnosis first.
- Keeping sparks out of fuel tanks. In 2001 the FAA’s Special Federal Aviation Regulation 88 required the holders of airliner designs to show that their fuel tank systems could not contain ignition sources. It also required new maintenance and inspection instructions to keep it that way. Wiring inspections on older aircraft became much more thorough.
- Making the vapour itself safe. The FAA’s 2008 fuel tank flammability rule set limits on how long the tanks most prone to explosion may contain flammable vapour, or required a system to stop an ignition becoming catastrophic. In practice this means nitrogen-enriched air to inert the tanks. Passenger aircraft with high-flammability tanks could not be flown in passenger service after 2016 without such a system. New aircraft built after 2009 needed it from the factory.
- Detecting and fighting cargo fires. In 1998 the FAA removed the Class D cargo hold as an option for new designs. Existing Class D holds in passenger aircraft had to meet the detection and suppression standards of Class C holds by early 2001.
None of these fires had a single cause, which is the point of the Swiss cheese model. For the full findings, the reports are listed below, and How to Read an Air Accident Final Report explains how to find your way around them.
The three live cases compared
| Flight | Aircraft | Date | Where the fire was | Time from first sign to end | Outcome |
|---|---|---|---|---|---|
| Swissair 551 | McDonnell Douglas MD-81 | 16 October 1993 | Emergency power switch in the cockpit overhead panel | Landed 13 minutes after asking to return | All 95 survived; 15 minor injuries |
| TWA 800 | Boeing 747-131 | 17 July 1996 | Fuel vapour inside the centre wing tank | No warning; the tank exploded in the climb | All 230 killed |
| Swissair 111 | McDonnell Douglas MD-11 | 2 September 1998 | Insulation and wiring above the cockpit ceiling | About 20 minutes from first odour to impact | All 229 killed |
Sources
- Transportation Safety Board of Canada: Air transportation safety investigation report A98H0003, In-flight fire leading to collision with water, Swissair Transport Limited, McDonnell Douglas MD-11 HB-IWF, Peggy’s Cove, Nova Scotia, 2 September 1998
- Flugunfalluntersuchungsstelle beim Luftfahrt-Bundesamt (FUS), Germany: Untersuchungsbericht EX 003-0/93, Swissair Flight 551, MD-81 HB-INH, Munich, 16 October 1993 (German; hosted by the Swiss Transportation Safety Investigation Board)
- National Transportation Safety Board: Aircraft Accident Report NTSB/AAR-00/03, In-flight Breakup Over the Atlantic Ocean, Trans World Airlines Flight 800, Boeing 747-131, N93119, July 17, 1996
- National Transportation Safety Board: Aircraft Accident Report NTSB/AAR-86/02, Air Canada Flight 797, DC-9-32, C-FTLU, Greater Cincinnati International Airport, June 2, 1983
- National Transportation Safety Board: Aircraft Accident Report NTSB/AAR-97/06, In-Flight Fire and Impact with Terrain, ValuJet Airlines Flight 592, DC-9-32, Everglades, May 11, 1996
- Federal Aviation Administration: Improved Flammability Standards for Thermal/Acoustic Insulation Materials Used in Transport Category Airplanes, final rule, 68 FR 45046, 31 July 2003
- Federal Aviation Administration: Transport Airplane Fuel Tank System Design Review, Flammability Reduction, and Maintenance and Inspection Requirements (SFAR 88), final rule, 66 FR 23086, 7 May 2001
- Federal Aviation Administration: Reduction of Fuel Tank Flammability in Transport Category Airplanes, final rule, 73 FR 42444, 21 July 2008
- Federal Aviation Administration: Revised Standards for Cargo or Baggage Compartments in Transport Category Airplanes, final rule, 63 FR 8032, 17 February 1998
Last checked 31 October 2026.