rocky, ujm, and maybe others are not understanding me. An airline may impose any rule it wants. The question specifically was whether the federal law forcing the passengers to wear masks, as well as the airline to enforce said law, is unconstitutional.
Further, the question wasn’t whether it’s constitutional to set laws upon an airplane, such as requiring wearing pants. The question was whether prohibiting the travel, including entry into the country or a different state, was unconstitutional.
So the answer seems to be that airline commerce is different. Thanks, GH, CTL. I’ll research that and speak later.