Jet planes cannot fly in space primarily due to their reliance on atmospheric oxygen for combustion in jet engines, which are designed for propulsion within the atmosphere. While a jet engine could theoretically operate in a very thin atmosphere, it would lack the necessary thrust, maneuverability, and cabin pressure to function effectively in space. Rockets, on the other hand, carry their own oxidizers and are designed for the vacuum of space, making them suitable for space travel. The distinction between jet and rocket engines lies in their propulsion systems, with jet engines requiring atmospheric air. Ultimately, a jet plane's design and operational principles limit its ability to function beyond the atmosphere.