Confirmed Fire on board an aircraft, especially when it is in flight, represents one of the most feared hazards in aviation. Fire in the air can ultimately lead to loss of control, either as a result of structural or control system failure, or again as a result of crew incapacitation; Fire on the ground can take hold rapidly and lead to significant casualties if evacuation and emergency response is not swift enough.
Smoke or Fumes, whether they are associated with Fire or not, can lead to passenger and crew incapacitation and will certainly raise concern and invite a response.
Finally, a Post Crash Fire, following an aircraft accident, accounted for approximately half of all fatalities in in the period 1999 - 2007 (UK CAP 776).
Refuelling and Defuelling Risks: The kerosene fuel used by turbine engine aircraft has a higher flash/ignition point than the aviation gasoline used by piston engine aircraft but there are still potential hazards. The primary risk is unintended ignition of fuel vapour.
Fire in the Air
See Fire in the Air and guidance for flight crew and air traffic controllers:
The special case of Wing Fire is usually the result of fuel fed fire originating directly or indirectly from the malfunction of engines embedded in the wing but may also arise when wing mounted engines suffer an uncontained failure and wing damage is caused by the ejected debris.