Originally Posted by MilesMaxamillion

I agree with what most people have said, and I don't think it should be done as a big spectacle on a plane involving the FAs, an announcement, etc.

But, a less-pressure scenario would be to propose on the plane privately, and (assuming your GF's answer is yes) see if your GF would want the rest of the plane to know about the special moment. At that point, you could mention it to the FAs.