WASHINGTON — The competition to replace the US Air Force's Joint Surveillance Target Attack Radar System (JSTARS) fleet is officially underway.

The service Aug. 7 awarded the trio of competitors in the program each a pre-engineering and manufacturing development contract, for a total of $31.4 million.

The E-8 JSTARS is a modified Boeing 707-300 with long-range radars the Air Force says can locate, track and classify ground vehicles at a distance of up to 124 miles. There are 18 platforms in US Air Force inventory.

As the 707-300 is no longer being produced, the service has concluded that upkeep costs for the existing fleet will skyrocket in the future. Those costs, combined with advances in technology since the JSTARS entered service, are driving the decision to push ahead with a recapitalization program.

Three distinct teams, drawn from some of the biggest players in the defense industry, are taking part in the competition. The money will be put toward risk-reduction efforts and helping the companies prove out their offerings, as well as funding prototypes.

Lockheed Martin received just under $11.5 million under the pre-EMD contract. The world's largest defense contractor is teamed with Bombardier, which will provide a business jet option, and Raytheon, to help with the sensor integration.

Northrop Grumman, the incumbent contractor on the program, received $10 million in funding. Northrop is offering up a partnership with Gulfstream and its G550 business jet, with L-3 helping do integration.

While both companies are basing their designs around a smaller business jet solution, competitor Boeing is going larger, offering a modified version of its 737-700 commercial airliner. Boeing officials say they can win due to the extra space for crew onboard its offering. The Seattle-based company was awarded just over $9.9 million for its pre-EMD phase.

The goal for making the new fleet operational is 2023, which would make 2017 a likely time frame for a winner to be announced.

"We've contracted with these companies so they can bring their proposed solutions up to the Preliminary Design Review stage to prove design concepts," William LaPlante, assistant secretary of the Air Force for acquisition, said in a statement. "We're getting them working on activities to continue system engineering flow down and identifying the high risk items. Then, we can compete a development contract with high confidence in our requirements."

A potential roadblock for the program, however, is if Congress fails to pass a budget resolution. If the Pentagon is forced to operate under a continuing resolution or falls to sequestration-levels of funding, the competition may well end up being pushed to the right.

Correction 8/13/15 -- the original version of this story identified the 737-700 as the same basis Boeing uses for its P-8 aircraft. The P-8 is based on the 737-800.

Twitter: @AaronMehta