It's quite simple, just manage to get yourself off the ground, try holding W and D or W and A for as long as possible once in the air and you'll get trapped going up continuously as shown below.



Now all you have to do is simply ALT+TAB out and wait for about 35 hours. By which point, you should have enough points to clear all 5 achievements at once.

I'm not entirely certain if these values are correct but from my own experience they are as follows:
Rookie: Pilot - 5 Points
Pilot: EP - 100 Points
Pilot: CP - 400 Points
Pilot: Master - 800 Points
Pilot: Instructor - 1500 Points

You get 1 point for every minute of airtime. You can find your total points count on the main menu, so you can quit and come back whenever you need to play something else or turn off your PC.

Happy Flying!