More targets!
Somthing which I have longed fore and seemingly are absent in this game are destroyable structures. It would be fun to go on a bombing raid with other players destroying enemy baces and airports.

Multiplayer missions!
Also online missions! It would be fun to enable missions in servers so that the game itself would be more enjoyable! Like destroying the USS beast with buddy's or shooting at bandits. Having random multiplayer missions pop up would make playing together a lot more enjoyable.

Competition mode

It would be fun to make a competition mode where planes with a certain amount of XMLing and part count take a certain amount of spawn points which the player only has a certain amount off when spawning in for the first time.

Solo competition

Dogfights in simpleplanes have always been fun, so how fun would it be to do dogfights against other players!

The rules
The game would start with opponents having to build a plane from scratch as fast at possible with the two players only having a certain amount of building points to use, that is so that the players need to get creative and use the points that they have sparingly. Then after five minutes the game would start the one who doesn't get shot down will win!

Teams based competition

The rules
The teams would consist of teams of five, there would be two teams, a blue and a red one. The goal would be to destroy the opposing teams airport/ base. When the players spawn in they will only have a small amount of spawn points. When an opponent gets shot down or crashes they will be able to respawn at there own airport after a certain amout of time.
The spawn points keep getting higher for the longer that the game lasts. With higher spawn points the opponents may take bigger planes with better engines and more part count. The game ends when the two teams destroy of each other's bases/airports