Shuttle Discovery was the third orbiter built by NASA and has had over 20 years of upgrades and experience. It has flown 34 missions, most to the International Space Station, and is one of the most trusted shuttles in the NASA fleet. Discovery's 2006 Return to Flight mission brought Expedition crews to and from the ISS, but had problems with foam shedding that were similar to the Columbia disaster. The mission returned safely on July 17, 2006.