On September 25, the U.S. Air Force's new KC-46A will start to take off and have its first flight. The aircraft is an aerial refueling tanker made by Boeing Co.

The flight was announced Tuesday by Brig. Gen. Duke Richards during the Air & Space Conference near Washington, DC.  The development for the eventual successor to the KC-135 and KC-10 was originally planned for the spring as reported by Defense Tech.

"Once that first flight occurs we'll go into initial air worthiness," he said. That means the second flight will begin testing the boom, hose and drogue systems, he said.

The preparation for the first flight had been paused for a month due to a chemical mix-up that contaminated the integrated fuel system. Any scheduled margin built into the programme is already gone.

Boeing has already used its schedule margin and cash reserve and declared two charges for cost overruns with industry analysts forecasting a third charge next year.  First flight delays caught the attention of the Pentagon Congress and senior leaders, and it's a milestone Boeing will be keen to put behind it.

The first KC-46A is expected to begin passing fuel in January or February 2016 after a few a few months of general flying, according to the latest program schedule presented by Richardson. And as part of its test program, the aircraft tanker will pass fuel to F-16, C-17, F/A-18, A-10, AV-8B and another KC-46A.

Boeing Co. plans to deliver the first 18 KC-46A of the 149 aircraft tankers to the Air Force by August 2017.  The service has an estimate of $49 billion to build and develop all of the planes as a substitute to its aging KC-135 fleet, according to the budget documents of Pentagon.  A forecast of $80 billion was made by Boeing for the global market of new tankers, according to Trading Alpha.