DM wrote:

snipped

thank you to everyone who replied. I've been considering all the
explanations offered and appreciate the information. I'm pretty close to
accepting the "optical illusion" idea but am not quite there yet. I was
looking hard at that plane because I really didn't want to believe what
I was seeing. If it weren't for the fact that I could read the name of
the carrier on the plane, I'd probably be going for a UFO explanation!

Fly safe everybody.

Debbie