Eject! Eject! Sadly, Ace Combat 7: Skies Unknown doesn't have option to eject. That is why you should don't allow the enemies to shoot you down at all cost. This page will help you avoid enemy missiles and cannons.
When the HUD turns red and you hear the alarm about the incoming missile, you have a few options to avoid damage. Actions allowing you to avoid missiles and fire can be divided into:
Active dodges are the maneuvers you do to lose a missile. In Ace Combat 7: Skies Unknown, you only need to perform a few dodging maneuvers to silence the alarm. The only problem is that your enemy will shoot one missile after another. Remember, missiles can be fired at you by enemy aircraft and from the ground by anti-aircraft weapons SAM (Surface-to-Air Missile).
In general, the majority of your maneuvers during a dogfight to get behind an enemy's back will also serve as dodges. When your damage meter is close to 100%, every incoming missile will be a huge threat.
Avoiding Air-to-Air Missiles (AAA) isn't difficult. Don't fly too close to them, and with low speed. If you are forced to fly above them, do that fast while changing your flying course constantly.
Passive dodging are all actions done by your aircraft independently from you to avoid enemy missiles. The most basic ones are chaff & flares that can be shot out from your aircraft. However, leave them as your final option - every aircraft has only a few sets of them.
Another method to avoid getting shot down is to install the right parts. Some of them increase your stealth, e.g. Onboard Self-Defense Jammer. Automated Fire Extinguisher will always repair your aircraft and reduce the damage level back to 50%.