I was sat on a Jumbo at Heathrow (en route to Reno Air Races) - we had just felt the slight jolt of the Tug attaching when we were told about a delay but fortunately somebody had a personal radio on so we did hear a little about the attack.
We also visualised an accident at first - eventually we were offloaded into a chaotic Airport and I just got a taxi home - couldn't face the huge queues for public transport !
Felt absolutely gutted for the victims/families - the footage really was bizarre/surreal !
I went back to work for a few days and flew out on the sunday to a very different holiday than originally planned - even managed to get a ride with the late Larry Stoffel in his 1928 Travel Air Biplane out over Tillamook Bay (the Lord only knows how he kept flying when [almost ?] all civvy a/c had been grounded).