The best i've seen was a meteorite. Holding point at EGBO, summers day, half the sky overcast at several thousand feet, the other half clear blue. Out of the cloud streaming down at 45 degree angle yellow/silver flame with white tail. At first thought it was an aircraft on fire, but the speed was way too fast. The t/l sat next to me didn't see it, nor anyone else i spoke to on the airfield.