Novastrike

Sounds simple but there's a lot going on is this stage and it can become overwhelming. Visit this thread for discussion. In it, Lieu10ant provides this strategy:

Fly North East to the island that is directly above the red arrows when the level starts and start attacking the island from the left side. There are less enemies that can hurt you. You should be done with this island before you fail the first objective but if you don't, then you might want to restart the stage.

On the 2nd island, attack from the South and only the South. Plant mines near the generator and keep using the Vulcan cannon and the regular ground weapon. Use the attack to kill enemies that fly around.

For the 3rd island, fly directly south from the previous island. Now when you get pretty close to it, stay 2 Kilometers away from the island and fly around it to the south (from the right side). Now, when you are on the south side of the island, just kill off the generator again.

When you are done with this island, the aggravators (suicide bombers) should be launching. Before you fly to the 4th island, kill those off immediately. Don't waste all the time you've worked for to be killed by these. Now just attack the 4th island from the right side (you don't have to kill any ground enemies because they wont affect you. Make sure you use your mines.

Now go to the portal and the big ship should be arriving; kill it first and then finish the level off by destroying the 4 'legs' attached to it.