I don't think it's upside down but "backwards" (field of stars on the right, stripes to the left).

This is to give the impression of a "flag in motion". Imagine someone running forward with a flag held up. If you look at them from their left, the flag is oriented normally). If you look at them from the right, the flag is "backwards" (blue field to the right, stripes to the left).

The airplane in question probably has its flag oriented the same way. Correct on the left side, reversed on the right. U.S. Army soldiers wear their shoulder flag patches the same way.


An upside down flag is a universal symbol of distress.