However, multi-engined aircraft - like the one that crashed - can be provided with ATC clearance to fly elsewhere in the London Control Zone.

BBC: London helicopter crash: What are the rules for pilots?

SpaceX was quick to make the point that the ability to carry on despite an engine failure demonstrates a big advantage of multi-engined rockets like the Falcon (Space Shuttles and Saturn V moon rockets could both do something similar).

ECONOMIST: SpaceX goes to the ISS