Alas, never got a shot of it. Lots of ho-hum shots of the horizon and some neat clouds but nothing memorable. Usually any worthwhile event was gone before being camera-ready. It was easier and more fun to compose poetry(!).
This is a fully round rainbow. The only way to see it is to fly low above a flat cloud cover, an undercast.
'The clouds have to be flat so they make a deck for you to fly above. You roll up in a turn so that the sun is coming through the canopy of your plane and falling on the cloud deck below. That casts a perfectly circular rainbow with the silhouette of your airplane exactly in the center. - Danny Cox, There Are No Limits.'