MechWarrior 5: Clans

You fight the Gazelle dropship during the "No Holds Barred" mission on Courchevel. It will be circling the airfield, firing its weapons down at you. Once you take out all its weapons, it will retreat. Do this twice, and on the third time it returns, you will be able to kill it. Its weapons get progressively more dangerous - the first time it pops up, for instance, it has Large Lasers and AC/10's, but on its last run it will have Gauss Rifles and PPC's.