You just have to survive until you reach Group B to win.

Only hunt strafers when the ground menace is distant.  The steep canyon walls will be a worse enemy to them than you can hope to be.

Watch to see who’s attacking who.  Make protecting yourself priority one, but help your friends too...their guns can help you a lot.

Take out the mobile cannons as soon as you see them.  One hit from them can ruin your whole day.