Snoopy Flying Ace

A general strategy I used for all missions concerning dogfights (against other planes) was to equip SQUITOS. I like Wingman as a second weapon. Whenever you see a group of enemies coming your way, drop the SQUITO bombs as they pass through you. You will take out as many as 3 at a time. Also, when they are on your tail, drop some SQUITOS and then press A (turbo). Do a 180 loop (down on the right stick), and drop some more SQUiTOS as the enemies pass through you.

BULLY FIGHT - Use a Heavy plane as the Machine Gun is stronger. I used the Squito strategy above and Wingman. Make them follow you and drop the Squito bombs, then do 180 loop and drop more bombs when they pass through you. Focus on not dying. You can easily do the <5:00 minute mark. These ones are straight forward.

ZEPPELIGEDDON - Use a Heavy Plane. If you are wondering which weapon does the most damage to the Blimp, try using the Molten Flail as you pass on top of it, or try to hit it from the side. Silver Bullet is good too. However, I found that using these weapons takes away from the dogfights as the weapons are hard to use against other planes. I used Squitos/Shotgun and Wingman. As soon as the Blimp is red use your Machine Gun and fire Wingman from a distance. When you get closer, use Shotgun, and if you chose Squitos, get close to it and drop the bombs. The Squitos will stick to the Blimp. Try to be fast when the Blimp is red as this is when he will get closer to your Headquarters. When you have one enemy left, pay attention to the distance from the Blimp. You don't wanna be really close to it as you won't be able to shoot it well. After it gets it's shields up, use the next few seconds to position yourself close to the front, where planes are going to come out. If you have the Shotgun, fly parallel to the Blimp. As the planes come out, use your Shotgun to take a few of them out, then position yourself in front of the Blimp (as if you were one of them). More planes will fly you by and you can take them out as they pass.
If you chose Squitos, do the same but position yourself right in front of the exit, and drop the bombs so you kill them as they come out. Go for No Deaths and Time.

BOMBS AWAY - Really Easy. Keep an eye on the ground targets so you don't miss any. When you start to get hit by planes, switch and use your Machine Gun and LT to fire rockets which take planes out almost immediately.

You can check the criteria for getting 3 gold medals in-game by pressing Start and then Objectives.