The U.S. Naval Air Systems Command (Navair) earlier this month released a final request for proposals (RFP) for the MQ-25 Stingray unmanned refueling aircraft. The command expects to award an engineering and manufacturing development (EMD) contract to one of four competitors by next fall.

Navair issued a brief statement confirming the RFP release, which occurred on October 4. “The purpose of the EMD effort is to design, develop, deliver and test the air system, and to integrate it with the overall MQ-25 system,” the command said. “Contract award is planned for late Fiscal Year 18,” which runs this month through September.

The command released the RFP to four companies—General Atomics Aeronautical Systems, Boeing, Lockheed Martin and Northrop Grumman—that have had Navy contracts since 2011 to study the air vehicle, which the service originally envisioned as a surveillance and strike platform. The overall program consists of air vehicle, control system and carrier segments.

In 2016, the Pentagon directed the Navy to refocus the effort to produce a carrier-based unmanned refueling tanker. That mission is now performed by Boeing F/A-18E/F Super Hornets, multirole fighters that due to current operations are burning through their 6,000-hour service lives.

The Navy and competing contractors have released little information about the air vehicle development. In an interview published in September by the U.S. Naval Institute Proceedings Magazine, Vice Adm. Mike Shoemaker, Naval Air Forces commander, said the MQ-25 will extend the range of carrier air wings “probably 300 or 400 miles beyond where we typically go,” and help reduce fatigue on Super Hornets. F/A-18, EA-18G Growler, F-35C Lightning II and E-2 Hawkeye pilots will fly the new drone.