The small square buttons on the left are the hangar and spawn point locations for your field.  Clicking one of these buttons puts you on the runway or spawn point in your currently selected plane, vehicle or boat with your previously selected ordnance and fuel load.

The Tower option moves you to the Control Tower if you are in another field location such as the Hangar or O'Club.  Clicking the Ships option will bring up the interface for Player Controlled Task Groups.

The O'Club option moves you to the O'Club where you can change countries, change your game id or set up a squad.

The Hangar option moves you to the hangar where you can select a plane, vehicle or boat, change ordnance and fuel loads, set the convergence of your guns, or check your Perk Points.

The Roster option will show you all players currently online, their rank and squad affiliation.

The Options button shows the game setup options on the clipboard and this is where you can map the keys on your keyboard, map the buttons on your joystick and calibrate your joystick to work with Aces High.

The Quit button will exit Aces High and return you to your desktop.