Fly, You Fools! Achievement in Halo: The Master Chief Collection

This achievement can only be earned on the Legendary difficulty.

After clearing the firefight against Covenant forces at the start of this mission, you will eventually encounter a UNSC Scorpion tank. From here, there are two hidden switches that must be pressed quickly in order to magically spawn four Covenant Banshees for use. Because there are two switches, and the second switch must be activated quickly after activating the first, this achievement will require either a second controller or another player.

Please refer to the video guide below, courtesy of Halo Completionist, for more information regarding the location of the switches and the Banshees.