The Air Force selected General Electric [GE] and Pratt & Whitney [UTX] to move forward in its proposed development program to improve the performance of next generation combat aircraft engines.

The Air Force awarded General Electric a $349.7 million indefinite delivery, indefinite quantity (ID/IQ) contract Friday as part of the proposed Adaptive Engine Technology Development (AETD) program. GE spokesman Matt Benvie confirmed Monday the contract was for the AEDT program. Pratt & Whitney confirmed in a statement it was selected to move forward in the AETD program, but company spokesman Matthew Bates said yesterday the company is still negotiating its contract.

AEDT is designed to improve combat jet engines’ fuel efficiency, durability and thrust performance. The program will also include un-refueled range for several platforms engaging in Anti-Access/Area Denial (A2/AD) environments.

Rolls-Royce also entered a bid for the program, but was not picked.

“We are disappointed by this decision, but Rolls-Royce continues to work with the Air Force Research Laboratory (AFRL) on important programs such as ADVENT and HEETE,” a company spokesman said yesterday in a statement. “We at Rolls-Royce invest significantly to ensure our technology is at the cutting edge and we will continue to actively discuss ways in which our advanced technology may benefit our customer in the next generation of airframes.”

ADVENT, or Adaptive Versatile Engine Technology, is an Air Force program considered to be AETD’s predecessor. Technologies demonstrated through ADVENT that will be validated by AETD include an innovative adaptive three-stream fan, third stream-cooled cooling air and ceramic matrix composite materials (CMC), according to a GE statement. GE and Rolls-Royce are both working on ADVENT but are not teamed together as both companies have separate technologies and contracts, according to a Rolls-Royce spokesman.

Highly Energy Efficient Turbine Engine (HEETE) is an Air Force technology development program that pursues high temperature, high pressure ratio compressor technologies and their related thermal management features, according to a Rolls-Royce statement. Both GE and Rolls-Royce have separate HEETE contracts as well, according to a Rolls-Royce spokesman.

Phase 1 of the AETD program, which runs through mid-fiscal year 2015, includes completing preliminary design, testing a full annular combustor rig, high-pressure compressor rig and components using CMCs, according to a GE statement. Phase 2 of the program, to be completed in FY ’16, consists of fan rig testing and a full engine core test, allowing for a notional first full engine test as early as 2017.

Pratt & Whitney is a division of United Technologies Corp. [UTX].