I used the Very Thin/tainted code for Mars due to it being carbon dioxide.., climbing out onto the wing of an airliner would just be Very Thin! I agree though, you'd need the same equipment to survive both... an oxygen mask and tank.
I would agree that Mars should get a thin atmosphere, though I'm not sure it would also need to be considered 'tainted'. Being so thin you would need (probably) the same gear that a tainted one would (or perhaps more, since its so thin, and you could have a standard earth's atmosphere that was tainted and you just needed a filter).
Paul Elliott ORBITAL
: The Solar System Setting for Traveller, a hard setting full of TL 9 technology, rockets, landers, Orion capsules and colonies on Mercury, Mars and the moons of Jupiter and Saturn. http://zozer.weebly.com/orbital.html