The KC-46A Pegasus tanker has received Milestone C approval from the Pentagon, clearing the way for the aircraft to enter production.

After approval was granted by Frank Kendall, under secretary of defense for acquisition, technology and logistics, work is now underway to award the first two low-rate initial production lots in the following month, the U.S. Air Force said in a statement.

Securing approval required the Pegasus to complete several aerial refueling demonstrations, including the refueling of an F-16 Fighting Falcon, C-17 Globemaster III and A-10 Thunderbolt II off the boom.

It also required refueling an AV-8 Harrier II and F/A-18 Hornet off both the hose and drogue systems.

The Pegasus also had to prove its receiver capability by taking fuel from a KC-10 Extender.

Some demonstrations were delayed due to higher than expected axial loads in the boom, the service said.

Boeing installed hydraulic pressure relief valves to alleviate loads, and all remaining demonstrations were completed, the Air Force said.

The Air Force will soon award contracts to Boeing for two lots, totaling 19 aircraft, in a deal worth $2.8 billion that will include associated spare parts.

The first aircraft will be delivered to McConnell Air Force Base in Kansas and Altus Air Force Base in Oklahoma.

A total of 18 tankers are scheduled to be delivered by early 2018.

The KC-46 still needs to complete a schedule of Federal Aviation Administration and military certification flight testing that includes refueling test flights.