A test explosion on a Boeing 747 suggests that a US Christmas Day flight would have landed safely even if a bomb on board was detonated successfully.
The test plane's fuselage did not break in the controlled blast, which used the same amount of explosive allegedly carried by Umar Farouk Abdulmutallab.
Mr Abdulmutallab, 23, has denied attempting to murder 289 people by trying to blow up a flight to Detroit with a device hidden in his underwear.
The experiment was carried out by UN explosives expert Dr John Wyatt and analysed by air accident investigator Captain J Joseph.
How safe are our Skies? Detroit Flight 253
is broadcast on BBC Two on Thursday 4 March, at 2100 GMT. Watch for 7 days after that on
Plane survives 'Flight 253-style' bomb blast