If you get out onto the runway with an La-7 and, instead of turning on the engine, you hold down the following combination of keys -- windows, alt, ctrl, shift, @ then hit F1 -- you activate "weather-balloon launch mode." Basically, it hooks your La-7 up to a giant high-altitude weather balloon that tows the plane up to as high as 100,000 ft. At any time between launch and 100,000 ft, you can disconnect from the tether, start your engine, and be cruising around.
I've used this technique to get my La-7 up to 95,000 ft., although the handling is somewhat sluggish at that altitude unless I turn on the optional La-7 JATO pack to get my speed up to a more comfortable mach 1.7.
