for eight Cygnus flights, covering deliveries to 2016. The first operational resupply missions were flown by SpaceX in 2012 (CRS SpX-1) and Orbital in 2014 (CRS Orb-1). In 2015, NASA extended CRS-1 to twenty flights for SpaceX and twelve flights for Orbital ATK.

A second phase of contracts (CRS-2) was solicited in 2014. CRS-2 contracts were awarded in January 2016