the mcdonnell douglas yc-15 was a prototype four-engine short take-off and landing (stol) tactical transport. it was mcdonnell douglas' entrant into the united states air force's advanced medium stol transport (amst) competition to replace the lockheed c-130 hercules as the usaf's standard stol tactical transport. in the end, neither the yc-15 nor the boeing yc-14 was ordered into production, although the yc-15's basic design would be used to form the successful mcdonnell douglas (later boeing) c-17 globemaster iii.