Usage and Grammar

Q. I work for an insurance company, and one of our beloved underwriters is disputing an exclusion in our policy that specifies “while piloting or serving as a crewmember in a plane.” She wants it to read, “while piloting or serving as a crewmember on a plane.” I can think of ways to defend both, but I’d love to know which is correct.

A. In English it’s rare that there is only one correct way to say something, but if you think that “on a plane” could technically mean sitting on top of the plane, that would be a pretty exclusive exclusion.