EVERETT — Boeing workers are hustling to get the first test plane for its aerial-refueling tanker program into the air sometime in the second half of November — about five months later than the company had planned.

Boeing is testing wiring it had to remove from test planes, redesign and reinstall, causing the delay. The aerospace giant won’t say how close it is to getting the airplane into the air.

But the Air Force general who until last week oversaw the tanker procurement program said that the first test flight won’t happen before mid- to late-November.

That first test plane won’t yet be a fully configured tanker when it first flies. It will be a 767-2C, an interim design based on Boeing’s successful passenger jet, the 767-200ER.

A full militarized version, the KC-46 Pegasus, is expected to fly in April 2015, Lt. Gen. John Thompson said at an Air Force Association conference last month.

The Air Force ordered the new tanker, which can also serve as a cargo and personnel carrier, as a replacement for the aging KC-135, which was based on the Boeing 707.

Both the Air Force and Boeing say they are confident the company can deliver the first batch of 18 tankers by August 2017, a date set in the contract.

The Air Force did not respond by deadline to requests for comment. But “the next six months are absolutely critical for the execution of the program,” Thompson said last month.

Thompson oversaw the KC-46 program for the Air Force through the end of September. He was promoted and given a new command last week.

In less than a year, the Pentagon is to decide whether to start production.

The Air Force ordered 179 KC-46 tankers, a contract worth an estimated $41 billion. The planes will be built in Everett.

Boeing is designing and building four test aircraft for the program. Those planes will eventually be delivered and go into service. Next September, the Defense Department has to make a decision about building the rest of the tankers.

Thompson said he is confident Boeing can keep the program on track.

The KC-46 has a huge amount of wiring on board — about 120 miles in all. That is 50 miles more than the wiring aboard on a standard 767.

Much of the wiring is redundant. A critical system might have three duplicate sets of wiring. That way, if the first and second system failed, there is a third.

Federal safety standards prohibit back-up wires from being installed = next to each other. Doing so would defeat the purpose of having a backup. For example, an onboard fire could take out a system’s primary wires, as well as the backups if they are installed in the same bundle. Earlier this year, Boeing discovered that about 5 percent of the wire bundles on the four test aircraft were not separated as specified.

“They had inadvertently put redundant systems right next to each other, or too close to each other to meet the (Federal Aviation Administration) and the military standards,” Thompson said.

It isn’t clear where the bundles were initially designed and produced, but the redesign was done by Boeing engineers in metro Puget Sound, according to sources familiar with the program.

Boeing has focused on fixing the first plane. The other three aircraft are parked around Paine Field, awaiting their turn.

The company won the $4.4 billion development contract in early 2011. It is a fixed-price contract, meaning that Boeing has to cover any cost overruns.

In July, the company said it had to cover a $425 million pre-tax charge — $272 million after taxes — to resolve wiring and other problems.

David Strauss, an investment analyst with UBS, said he doesn’t expect another overrun charge when Boeing announces third-quarter earnings later this month.

“The margins for further cost creep are pretty narrow,” he said.

While the airplane is far less complicated than, say, a new fighter jet, “there is a lot of technology adaptation” from a commercial 767, he said. “There’s a lot of room for things to go off track.”

But Strauss and other analysts expect Boeing will make sure that doesn’t happen.

Boeing will keep five test labs set up for the tanker’s development, said Jerry Drelling, a company spokesman.

The labs will support the KC-46 after it is in production and future aircraft development, he said.

The 179 KC-46s are only the first batch. The Air Force has plans to replace the rest of its fleet of more than 500 tankers with two additional programs, called KC-Y and KC-Z.

The Air Force will start work on the KC-Y program sometime in 2017, with first delivery in 2028 or later, said Ed Gulick, an Air Force spokesman.

Dan Catchpole: 425-339-3454; dcatchpole@heraldnet.com; Twitter: @dcatchpole.