There’s only room for one pilot
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One of the more advanced cockpits in modern military aircraft, the F-22 is as high tech as it is cramped. It includes a monochrome head-up display, as well as a keypad system for entering communications and autopilot data, but only has space for one pilot.
As you might guess since pilots will have no co-pilot for recourse, only the most experienced ones are allowed to fly these beasts.