Air Marshals aren't the only weapon toting Marshals that fly. If any US Marshal flies whether for work or for vacation, they can and will carry their badges and weapons with them. They go through a separate security area, they meet the pilot as they are boarded first, the stewardesses also know they are there & where they sit on the plane.

But I agree, it sounds like Bidan wants them off planes for a different reason than helping at the border.