This is the first mission, complete the tasks and you'll be fine.
I did replay this mission and had two issues, First you can't destroy the helicopter when you get it, so don't accidently eject.
Second, when you get to the area with the tower (after flying the helicopter) you can break the dialog, just kill everyone and everything and the game will finish the mission (that's what you're supposed to do but I got on the mini gun too fast on my second play through and I think I broke the mission script, the helicopter for instance was never in range of the mini gun)