World's Most Massive and Costly Military Aircraft Ever Built

7. Pegasus, KC-46

Entered Service in 2019 Not retired: N/A Cost: $189.4–$250.2 million The KC-46 Pegasus is an aerial refueling aircraft designed by Boeing and named after the winged horse of Greek mythology. In addition to refueling, the Pegasus is used for strategic transportation of military equipment. It was developed as part of the USAF's KC-X tanker competition.

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KC-46 Pegasus / Pinterest / hal_cohen The Pegasus was designed to replace the aging KC-135 Stratotanker. First delivered in January 2019, it is one of the most modern aircraft on this list. The USAF plans to acquire 179 units by 2027, with a total development cost of $241.2 million.