The Airports Add-on for Cities: Skylines - Remastered has 5 achievements worth 150 gamerscore.
Have an airport area reach level 3.
Have 10 000 total passengers travel through an airport area.
Build an airport area with a terminal, a runway and an aircraft stand.
Build an airport area with an area of 25 000 cells.
Set the airline ticket price slider to the maximum price.