The 747's first commercial flight was on 22 January 1970, a Pan Am service from New York to London, which was delayed six hours because of an engine overheating. There were other less well-publicised problems. The size of the plane meant evacuation drills were fraught. First attempts took two and a half minutes. It was only possible to get it down to the FAA mandated 90 seconds with the acceptance of more injuries during the evacuation. Early models suffered from flutter, a self-exciting oscillation that can lead to catastrophic destructive failure. It was fixed by the fantastical Cold War remedy of putting lumps of depleted uranium in the outer engine nacelles. The El Al cargo 747 that crashed in Amsterdam in 1992 was carrying 282 kg of depleted uranium in its tailplane for reasons of stability.
