Reward: Top 5 Shortest Runways
Difficulty: Easy
Estimated Time: Varies
As you can see in the image, you have to land at 0WN5, OH41, LA07, LS93, and 67NY to receive this reward. These airports have the shortest runways in Flight Simulator X. I found it best to start at each airport and then takeoff, rather than trying to find them after leaving another airport. This way, you can orient yourself from the ground, as they can be very hard to spot from the air.
Don't forget to land with an aircraft that doesn't require much runway. Ultralights and helicopters are well suited for the task.