The US Air Force has released a request for proposals for a contract to beef up the structures on on a subset of the Lockheed Martin F-16 fleet to keep the single-engined fighter in service for at least 30 more years.

In April, the USAF authorized a plan to extend the F-16C/D model’s service life from its original 8,000 flight hours to 12,000 flight hours. A June notice increased that extension to 13,856 equivalent flight hours.

The SLEP would keep up to 300 Block 40 through Block 52 F-16s flying beyond 2048, with an option to extend the requirement to 489 F-16s.

The contract has a $403 million ceiling, according to the 20 November RFP. The USAF intends to start procuring structural modification kits in 2018, which will also be available to foreign military sales customers, the notice states.

Though original F-16 manufacturer Lockheed celebrated the approval of the SLEP programme in an April press release, the recent RFP is a small business set-aside solicitation and disqualifies Lockheed from bidding for the work.

This article has been edited for clarification to note the small business set-aside construction of this contract.