Sierra Nevada Corp. (SNC) announced July 19 that it has picked the United Launch Alliance (ULA) Atlas 5 rocket to launch the Dream Chaser spaceplane’s first two cargo resupply missions to the International Space Station.

“SNC recognizes the proven reliability of the Atlas 5 rocket, and its availability and schedule performance makes it the right choice for the first two flights of the Dream Chaser,” said Mark Sirangelo, corporate vice president of SNC’s space systems business area.

According to ULA, a joint venture of Boeing [BA] and Lockheed Martin [LMT], Atlas 5 has achieved 100 percent mission success since its debut in 2002.

The first Dream Chaser mission to the space station is set to lift off in 2020 from Space Launch Complex 41 at Cape Canaveral Air Force Station in Florida. The second mission is scheduled to lift off in 2021.

SNC was one of three companies chosen in 2016 to transport cargo to and from the space station under NASA’s Cargo Resupply Services-2 (CRS-2) contract. The others are Orbital ATK [OA], with its Cygnus spacecraft, and SpaceX, with its Dragon capsule. NASA has said that each company is guaranteed a minimum of six missions.