Having heard various theories as to why said "Rapture" (overheard yesterday
) needs an escort, it would be nice to hear some firm reason.
I suspect (although don't know for sure) that the F-22 currently doesn't have the required avionics fit (Mode-S) to transit through UK controlled airspace.. the escort aircraft probably does and would allow ATC to "see" the aircraft (don't forget that the F-22 has been designed to have a small radar cross section... so that it can't be seen by radar!)