Raytheon [RTN] and Italy’s Leonardo decided to jointly not pursue the U.S. Air Force Advanced Pilot Training Program, T-X, the companies said Wednesday.

The companies announced their intention to team together on the T-X pursuit in Feb. 2016, resulting in a model called the T-100  based on Leonardo’s M-346 Master. However, Raytheon spokesperson B.J. Boling said in a statement on Wednesday that “While we remain confident that the T-100 is a strong solution, our companies were unable to reach a business agreement that is in the best interest of the U.S. Air Force.” 

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“Consequently, Raytheon and Leonardo will not jointly pursue the T-X competition,” he added.

The T-X program aims to replace the Air Force’s T-38 pilot training aircraft and is one of the Pentagon’s few new start programs. Initial operating capability for the T-X is planned for 2024..

The Air Force issued a $16.3 billion development request for proposals (RFP) for the program in late Dec. 2016, laying the groundwork for delivery of the first five test aircraft with options for low rate initial production (LRIP), full rate production (FRP), and lots three through 11 for a total of 350 aircraft (Defense Daily, Dec. 30, 2016).

Other teams still intending to compete for the T-X include Boeing [BA] with Sweden’s Saab for a clean sheet design; Lockheed Martin [LMT] with Korea Aerospace Industries (KAI) for KAI’s T-50; and Northrop Grumman [NOC] with L-3 Communications [LLL] and BAE Systems for a clean sheet design.

The Boeing-Saab team first tested their offering last month (Defense Daily, Jan. 20, 2016) using a one engine, twin tails, stadium seating aircraft with an advanced cockpit and embedded training.

Lockheed Martin initially flight tested its T-50A in June 2016 (Defense Daily, June 3, 2016).

Raytheon did not reveal any further details on why it and Leonardo cancelled their pursuit of the T-X.