The Air Force has taken a step toward re-competing production of Global Positioning System (GPS) III satellites by releasing a draft solicitation for up to 22 spacecraft.

Industry feedback on the document, along with a recent industry day in El Segundo, Calif., “will inform a final request for proposal,” scheduled for release in fall 2017, the Air Force said July 21. The Air Force plans to award a contract in late 2018 and receive the first satellite in 2025.

Lockheed Martin [LMT] is already building the initial 10 GPS III satellites, the first of which is in storage awaiting its expected launch in 2018. In May 2016, the Air Force awarded contracts to Boeing [BA], Lockheed Martin and Northrop Grumman [NOC] to study the feasibility of producing the 11th GPS III space vehicle (SV) and beyond.

Those studies have “determined that viable, low-risk, high-confidence sources exist to conduct a full and open competition” for the follow-on satellites, the Air Force said.

Boeing and Lockheed Martin both said they plan to compete for the next batch of GPS III satellites. Northrop Grumman declined to comment.

Boeing “will offer a complete, lower-cost, resilient GPS III solution that will feature advanced digital payload technology to meet evolving mission needs,” said Enrico Attanasio, executive director of defense and civil programs for Boeing Satellite Systems.

“We plan to offer the Air Force an affordable, resilient, low-risk GPS III solution which is already in production and already well on its way to meeting many of the Air Force’s SV11+ requirements,” Lockheed Martin spokesman Chip Eschenfelder said. “Our flexible GPS III design can evolve and add new capabilities in a low-risk manner.”

GPS III satellites are designed to replenish the GPS constellation and provide more accurate signals, be more resistant to jamming and last longer than existing spacecraft.