No-Fly Zone Achievement in Halo: The Master Chief Collection

During the second mission, Halo, there are a total of four Covenant Banshees that can be found soaring high in the air. The first two will attack you immediately after crossing the long bridge-like structure in the beginning of the mission. Unfortunately, destroying one Banshee will usually cause the second to flee. If you want to try destroying both Banshees here, shoot each of them with the Assault Rifle until their wings are smoking, then use the Magnum to finish off each Banshee quickly.

The second pair of Banshees will attack you much later on after saving the first life pod of Marines and traveling across the open canyon. The Banshees here will not flee at all, so use any weapon you currently have to make short work of them. After three Banshees have been destroyed in this mission, the achievement will unlock.