The air force’s developmental next-generation tanker, the Boeing KC-46A, is expected to make its maiden flight 25 September, according to the service’s programme executive officer for tankers.

Preparation for the first flight paused for 30 days after a chemical mixup contaminated the integrated fuel system and any schedule margin built into the programme is long gone.

Despite several setbacks and an almost one-year schedule delay, Brig Gen Duke Richardson says the second engineering and manufacturing development (EMD) aircraft, the first functional tanker, is in fuel dock after receiving repairs and should be airborne by the month’s end.

Speaking at an Air Force Association even in Washington, Richardson says “we’re not struggling in terms of capability” and Boeing remains committed to delivering the first 18 aircraft in August 2017. “There’s a lot going right on the programme,” he says.

The air force is breathing a sigh of relief that KC-46 is being developed under a firm-fixed contract, since the total development cost to the US government is capped at $4.9 billion and Boeing is taking the fiscal hit from any cost overruns.

Boeing has eaten up its schedule margin and cash reserve and has declared two charges for cost overruns so far with industry analysts predicting a third charge next year. Delays to the first flight have drawn the attention of Congress and senior leaders within the Pentagon, and it’s a milestone Boeing will be keen to put behind it.

According to the latest programme schedule presented by Richardson, the first KC-46A is expected to start passing fuel in January or February 2016 after a few months of general flying.

As part of its test programme, the aircraft will pass fuel to a F-16, C-17, F/A-18, A-10, AV-8B and another KC-46A, according to Richardson.

A “milestone C” production and fielding decision is expected in April 2016 and two contract awards for low-rate initial production will follow in quick succession. The first low-rate production contract is for seven aircraft and the second buys a dozen tankers.

EMD-1, the 767-2C freighter the tanker is based on, has completed flutter testing and EMD-4 is scheduled to begin ground demonstrations later this month. Mission system verification demonstrations will continued through November, according to the updated schedule.