Cygnus OA-4 S.S. Deke Slayton II was the first Enhanced Cygnus spacecraft and the programme's return-to-flight mission after the Orb-3 loss. Launched on 6 December 2015 aboard Atlas V, it delivered more than 7,000 pounds of research and supplies to the International Space Station and completed destructive reentry on 20 February 2016.