the boeing yc-14 was a twinjet short take-off and landing (stol) tactical military transport aircraft. it was boeing's entrant into the united states air force's advanced medium stol transport (amst) competition, which aimed to replace the lockheed c-130 hercules as the usaf's standard stol tactical transport. although both the yc-14 and the competing mcdonnell douglas yc-15 were successful, neither aircraft entered production. the amst project was ended in 1979 and replaced by the c-x program.