Troops take so long to fall, they would of been around the world long before they hit the ground.
Now to get that high, what I did was take 100% fuel and take off from the highest base available. I set the autoclimb and wait patiently to get high enough for the turbojets to kick in (27,000 to 30,000 feet). Be warned, it can take upward of at least 45 minutes to get that high with 100% of fuel. Just leave it on autoclimb, and you will know when the turbo kicks in. The climb rate increases to roughly 3,000 to 4,000 feet per MINUTE. ALso fairly easy to maneuver once it kicks in also.
The limit to as high as you can go is only limited to the amound of fuel you bring. I have a film somewhere of dropping troops at 2000,000 feet. Hope this helps!