Uncanny X-Men #86

The X-Men arrive too late to stop the Mutant Master and his Factor Three organization from initiating events to start World War III. In the empty control room, they see a video of the Mutant Master mocking them about his impending victory. Acting on Beast's hunch, they escape in one of Factor Three's flying saucers just before the base explodes. As they fly away, the X-Men start planning how to prevent the Mutant Master from triggering another world war.