Once the game is full release, this forum (or the subreddit) should hold competitions.
Real Replications - Copy (as close as possible) a real Airport eg LAX, DFW, LHR etc.
Free Design - Design an airport any way you want. The best and most creative wins.
Constrained - Best airport following a design criteria (eg. Only small gates, seperated security areas, 1 tile)
The “public” can then vote on them and the winner could win a space on the leaderboard (or maybe even some Airport CEO merch in the future (?)).