[MineralMan]

"Are passengers allowed to bring their own oxygen on board planes, and to breathe it?"

Nope. Pressurized oxygen bottles are prohibited.

[safisoft]

"Are passengers allowed to bring their own oxygen on board planes, and to breathe it?"

Nope. Pressurized oxygen bottles are prohibited.

Not quite true. Becasue of FAA safety requirements (O2 is a flammable gas), the bottles have to be supplied by the airline and have FAA approval, but there ARE pressurized O2 bottles available upon request. Normally, when making reservations the request is made along with accompanying doctor's instructions etc.