Suspended Pelican

It is possible to see a Pelican dropship suspended in mid-air on the level, Metropolis.

Directions
Play through the Metropolis level until two Pelican dropships arrive, right before you meet Corporal Perez. The Pelican with the attached Scorpion Tank will fly above the building and freeze in place.

If you shoot rockets, Wraith plasma mortars or Scorpion shells at the Pelican (with the Sputnik skull) until it moves about 50 feet and then go up the staircases, the Marines (and Sergeant Banks) and the Scorpion will not be there. The Scarab will still briefly pause, but it will not shoot at where the tank normally appears.