A perfect ATC game for flight lovers with no crash detection!!! The yellow values are the incoming flights on your radar. Click on the yellow values to give them a new command. Type in HDG, SPD or ALT HDG stands for Heading (DSirection). SPD stands for throttle (Speed) ALT stands fro altitude (Height from sea level) When you type HDG, it will change its heading to your mouse pointer. When you type SPD, it will ask you to type the new speed to fly in. When ALT is typed, it will ask you to type the new altitude to fly in.