This info from earlier today based on information I saw in a German paper. They quote an aviation expert.
This post/thread: FR....'Real and Definite Threat' Caused BA Flight Cancellation..#573
The aeronautics expert Philip Baum, editor of the magazine "Aviation Security International", assumes there are detailed secret service tips. "I think they must have credible knowledge which indicates that certain airlines on certain routes are possible targets for terrorist attacks". It could be possible, however, that the USA could have demanded the presence of armed marshals on board and the BA pilots could have decided not to take off because of that.
"Frankfurter Allgemeine Zeitung"....British Airways streicht wieder Flüge
Translated by longjack
The article uses the quotes just as I have them, which makes it likely this guy said it, but, then again..
longjack