Airbus and Lockheed Martin [LMT] said Tuesday they have signed an agreement to jointly pursue U.S. defense aerial refueling opportunities.

This new effort comes years after Boeing [BA] beat Airbus to win the KC-46A Pegasus tanker for the U.S. Air Force. Previously, Airbus was working with Northrop Grumman to offer its model for the tanker in a previous iteration of the tanker competition.

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Now Airbus and Lockheed Martin said they will cooperate to provide aerial refueling services, focused around the Airbus A330 Multi Role Tanker Transport (MRTT) for any identified capacity shortfall and to meet requirements for the next generation of tankers. The A330 MRTT was Airbus’ offering in the KC-46A competition.

The KC-46A has been beset by a multitude of delays, first in the contracting process then in finishing flight tests, airworthiness certifications, and dealing with technical deficiencies. Boeing was expected to originally deliver the first tanker in early 2016, but now expects it before the end of this year (Defense Daily, Dec. 3).

The Air Force plans to buy 179 KC-46As to replace some of its refueling fleet but wants to also replace other tankers like the KC-10.

They said they will look into a “broad spectrum” of opportunities including ways to support critical near-term air refueling needs, including using a fee-for-service structure in a future Air Force tanker.

Fernando Alonso, Airbus Defence and Space’s head of military aircraft, noted the A330 MRTT has been chosen by 12 countries for aerial refueling, has been praised by major air forces, and has been proven in live operations.

“We are convinced that the combination of Airbus’ tanker expertise with Lockheed Martin’s extensive U.S. presence, has the potential to provide highly effective solutions for current and future U.S. military aerial refueling requirements,” Alonso said in a statement.

International buyers include the Australian, France, Saudi Arabia, Singapore, South Korea, the U.K., the United Arab Emirates.

Lockheed Martin president and CEO Marillyn Hewson said that “by combining the innovation and expertise of Airbus and Lockheed Martin, we will be well-positioned to provide the United States Air Force with the advanced refueling solutions needed to meet 21st century security challenges.”

The partners noted while Airbus has the experience building tankers, Lockheed Martin has long experience in systems integration, manufacturing and maintenance, and repair and overhaul operations with large aircraft.

“Airbus is an industry leader in the aerial refueling area, and Lockheed Martin is known for cutting-edge defensive technologies and capabilities. This is a great opportunity for our two companies to combine our expertise – cooperating to develop world-class solutions for critical needs around the world,” Michele Evans, executive vice president at Lockheed Martin, said.