The mod adds a challenge called Falling Platforms to the game. In this challenge, you and the NPCs are on platforms that begin to shake and fall over time. Your goal is to stay on the platforms and not fall off them for as long as possible. If you fall last or simultaneously with the other remaining NPCs, you win and are rewarded. NPCs will try to avoid shaking platforms.
The challenge is located at the entrance to the airport (see screenshot).