Take out enemy fighters
Go to the outside view of the B-17 and place the mouse pointer on the far right. A box should appear with some planes. The Americans are the planes next to the stars. The Germans are marked with + signs. Click on the German planes and take control by pressing M. Then, bail out. Use the [ and ] keys to get the entire squadron. Do this to every squadron to become fighter-free.

Get the P-51
To get the P-51 you just have to start out in mid to late 1944. Note the missions are harder.

Get the ME 262
Start a mission in mid to late 1944, then go to heavily defended areas.

Custom soundtrack
Replace the game disc with an audio CD during game play. The game only uses the CD-ROM for music. The music from the audio CD will play in the menus, but not during missions.