Atlas V launch vehicle, which powers its first stage with a single RD-180 engine that is expended after each flight. In response, the US Air Force has asked the Aerospace Corporation to begin evaluating alternatives for powering the Atlas 5 booster stage with non-RD-180 engines. Early estimates in 2014 were that it would require five or more years to replace the RD-180 on the Atlas V. Even though the Russian government could cut off the supply to ULA of imported RD-180 engines, the US Congress, with emerging support from the Air Force, has come around to a view that it would not be advantageous to the US government to start up a US production line to produce the RD-180, mainly because it would need a licence from the Russian government. However, the US Congress is advocating for the initiation of a new US hydrocarbon rocket engine program, to field a new engine by 2022. In June 2014, Aerojet Rocketdyne proposed that the US Federal government "fund an all-new, U.S.-sourced rocket propulsion system", the thrust kerosene/LOX AR-1 rocket engine. , Aerojet's early projection was that the cost of each engine would be under per pair of engines—not including the up to estimated development cost to be funded by the US Government. Aerojet believed that the AR-1 could replace the RD-180 in the US Evolved Expendable Launch Vehicle fleet, and that it would be more affordable. On 21 August 2014, the U.S. Air Force released an official request for information (RFI) for a replacement for the RD-180. The RFI seeks information on "booster propulsion and/or launch system material options that could deliver cost-effective, commercially-viable solutions for current and future National Security Space (NSS) launch requirements. Air Force Space Command (AFSPC) is considering an acquisition strategy to stimulate the commercial development of booster propulsion systems and/or launch systems for Evolved Expendable Launch Vehicle (EELV)-class spacelift applications." The day before, the United Launch Alliance had taken delivery of two RD-180s, the first since the Russian annexation of Crimea. It is not clear when or if the replacement of the RD-180 would start, and the RFI asked input for several options including similarity to the Russian engine, whether it would come in a new configuration and the use of "alternative launch vehicles" for the EELV mission. In 2014, RD-Amross were selling the RD-180s (to ULA) for $23.4m each. In January 2015, Orbital Sciences Corporation have