Before the Scarab tank is destroyed, find a chopper and proceed to the right of where you came from. There should be a door with purple pillars to your right. Drive up to one of the further pillars and park the chopper against it, then jump up onto the pillar and onto the roof next to you. Wait at the edge of the roof. When the Pelican lowers, jump onto it. The Pelican will fly across the map. You will fall through it and die.