You have to click on the planes to land them. The airstrip can only hold a few planes at a time, though, and bigger planes take more space. When the green bar at the airstrip is full, space has run out. If you try to land a plane on a full strip, it won’t listen to you.
Every time a plane takes off on its own, it carries cargo to be delivered to people in need. You can make a plane take off early to clear room on the strip, but it will take off without its cargo. You need to airlift all of the cargo (blue bar at the airstrip) before time runs out.
The fuel is always running down on all the planes, so keep an eye on that–when they run out of fuel, they crash, and you lose points.
Source code: choke_point
Built with Processing. Licensed under the GNU Public License v. 3.0