It has been nearly four years since the US Air Force made its selections for companies to launch military payloads during the mid-2020s. The military chose United Launch Alliance, and its Vulcan rocket, to launch 60 percent of these missions; and it chose SpaceX, with the Falcon 9 and Falcon Heavy boosters, to launch 40 percent.
Although the large Vulcan rocket was still in development at the time, it was expected to take flight within the next year or so. Upon making the award, an Air Force official said the military believed Vulcan would soon be ready to take flight. United Launch Alliance was developing the Vulcan rocket in order to no longer be reliant on RD-180 engines that are built in Russia and used by its Atlas V rocket.
"I am very confident with the selection that we have made today," William Roper, assistant secretary of the Air Force for acquisition, technology, and logistics, said at the time. "We have a very low-risk path to get off the RD-180 engines."