The KC-46, the next generation of aerial refueler, completed it first test flight Friday after months of schedule delays and cost overruns. The program will now begin in-flight tests of the airplane’s refueling equipment, Boeing said.

The maiden flight of a fully provisioned Boeing KC-46A Pegasus tanker aircraft took place out of Paine Field, Washington, on 25 September. During the afternoon flight, pilots checked the engines, flight controls and environmental systems and reached an altitude of 35,000 feet. This was the first flight of a KC-46A tanker-configured aircraft, following on-going flights of the program’s first test aircraft, a 767-2C.

The Air Force could still be prevented from awarding Boeing an LRIP contract, however, if the U.S. Congress in the coming days passes a lengthy “continuing resolution” instead of a budget, which would limit the government to prior-year funding.

Boeing said it would start aerial refuelling flights with a number of US Air Force aircraft before the end of the year, which would help pave the way for a decision in 2016 to move into low-rate production.

Charles Ramey, a spokesman from Boeing, told the Defense News that following the successful flight test, the company and USAF will conduct the next series of flight tests for the KC-46 program. Those flights, along with the mission systems demonstrations and a recently completed ground cargo handling test, will support the two organizations’ planned Milestone C decision in 2016. The first test flight was initially expected in late 2014. “This flight represents progress and brings us a step closer to fielding this much-needed aircraft”, Air Force Secretary Deborah Lee James said in a statement.