International Space Station program out of 28 flights have not been to the ISS, and only the planned Hubble Space Telescope servicing mission in 2009 will not be ISS-related out of 13 planned missions until the end of the Space Shuttle program in 2010). The Space Shuttle was retired from service upon the conclusion of Atlantis' final flight on July 21, 2011. NASA was reliant even at the time on some of the resupply contracts being fielded out to Soyuz and Progress and the other unmanned tugs, but it had launched a few years earlier into a program of aggressive development of commercial US
Space Shuttle program from the back of a specially modified Boeing 747, only for initial atmospheric landing tests (ALT). "Enterprise"'s first test flight was on February 18, 1977, only five years after the Shuttle program was formally initiated; leading to the launch of the first space-worthy shuttle "Columbia" on April 12, 1981 on STS-1. The Space Shuttle program finished with its last mission, STS-135 flown by "Atlantis", in July 2011, retiring the final Shuttle in the fleet. The Space Shuttle program formally ended on August 31, 2011. Before the Apollo 11 moon landing in 1969, NASA began early studies of space shuttle designs.