E-4B 75-0125 Brussels to Andrews AFB flew right over me FL310, not a cloud in the sky, not trailing - could not see it.
Ditto me a couple of years ago...
Didn't see the Swazi A340 but did see the A380 coming into Heathrow while sitting in a friend's garden... Saw OO-TMA as well, Plane Finder said it was a TMA A300 which I assume should have been OD-TMA... now with EAT.