Boeing is offering a militarised version of the 737-700 for the US Air Force's joint surveillance, target, attack radar system (JSTARS) replacement need, and is confident that the airframe can beat out smaller, business-class jets.

The 737-700 is the smallest version of the line, but is still 3m (10ft) longer, nose to tail, than a Gulfstream G550, says Rod Meranda, Boeing’s JSTARS head of business development.

Gulfstream plans to offer the G650 for the US Air Force programme, which is seeking a replacement for the Northrop Grumman E-8C JSTARS fleet, developed from Boeing’s 707 airframe. Bombardier likely will offer the Global 6000. Airbus, Cessna and Embraer also have potential candidate aircraft, but have not confirmed an intention to compete.

Procurement documents say the USAF seeks a business-class jet with a “significantly smaller and more efficient airframe” for its next-generation JSTARS. Meranda contends that the 737-700 is a business jet, if slightly larger than probable competitors.

The aircraft’s larger size allows margin for future growth, Meranda says. Its CFM International CFM56 engines are larger and more powerful than many business jet power plants, and therefore can provide greater power and cooling to the aircraft’s radar and associated systems, he adds.

“We’re not banking that the margin of growth is going to be the differentiating criteria,” Meranda says. “You have to have power and cooling. … When you put a sensor and eight to 10 people on board an airplane … all the comms, all the racks, you have to power all of that stuff. Smaller jets have a harder time, based on the size of the engines to go ahead and produce the power and the cooling.”

Concrete requirements have not been published, but are expected to materialize by the end of the month, Meranda says. Unanswered questions include crew requirements and how large the fleet will be. The current fleet is 17 aircraft, but the air force has said it may have to scale back by as many as five aircraft as mandatory budget cuts called sequestration return in fiscal year 2016.

The E-8C flies with a crew of 18. The air force wants to scale back to a crew of 10 plus one, not including a pilot and co-pilot. Without formal requirements to aim for, Boeing and other JSTARS competitors are prioritising affordability and speed to production, Meranda says.

With 8,000 737s worldwide, he stresses that the aircraft could be offered at an affordable price and that lifecycle costs also could be kept low. Boeing has orders for various 737 variants that will keep production humming through the 2020s.

The air force plans for its future JSTARS capability to become operational in 2022.