height is not the issue if you have the right gear. world record formation attempts exit from Hercs at up to 30,000ft no problem.
sure they do HALO jumps from a 141. you once again have that magic configuration of overhead wing and free door at altitude. i dont know what exit speed they'd use, but i can assure you it is not likely to be close to the stall speed required to safely clear the wing of most commercial jets.
there aren't many large aircraft in the world that you can safely exit from at high altitude. the 727 mentioned earlier is one of the few commercial jets that you can actually jump out of, they use them at the World Freefall conventions for the general public.
