That's certainly true - 5 eyes - at least - will all be sharing the intel. and i dont doubt the US sat flash detection making it credible.
but that rather makes it even more surprising that the other 4 eyes havent stopped their flights, to say nothing of their european partners (perhaps not up there in the intel world, they do at least nominally cooperate on terrorism etc).
Are we suggesting that they care less about their citizens?
Perhaps it';s basically been agreed that the British are at the airport and making it safer for the rest of them.