Boeing's KC-46 tanker lifted off for first flight on Friday, successfully meeting its latest deadline after months of schedule delays and cost overruns.

After a slight delay due to weather, the test aircraft took off in the early afternoon and landed four hours later at Boeing Field in Seattle, Washington, according to a company statement. During the flight, Boeing test pilots performed operational checks on engines, flight controls and environmental systems.

"Today's flight reinforces that we are moving in the right direction and are on track to begin planned Milestone C testing later this year," said Tim Peters, Boeing's KC-46 tanker vice president and program manager, according to the statement. "This is an aerospace industry first and the culmination of a lot of hard work by the team, including Boeing, our suppliers and the U.S. Air Force."

For the next series of flight tests, the team will deploy the refueling boom and then the wing aerial refueling pods to check for stability, company spokesman Charles Ramey told Defense News in an email on Friday. Full-up aerial refueling flights are planned as part of Milestone C testing, he said.

The successful flight will give a much-needed boost to the next-generation tanker program. Brig. Gen. Duke Richardson, KC-46 program executive officer, told an audience at the Air Force Association's annual convention earlier this month that the aircraft would complete first flight on Sept. 25, Boeing's latest goal since being forced to postpone the milestone after a mislabeled chemical was mistakenly loaded into the aircraft's refueling line during testing.

This was not the first time first flight has been delayed. The event was initially slated for 2014, then pushed back to April, then postponed again to later this summer.

The Sept. 25 first flight keeps Boeing on track for a Milestone C decision, formal approval from the Pentagon for production, between January and April 2016. Boeing must deliver 18 full-up tankers by August 2017.

In an effort to tighten Boeing's reins, Air Force Secretary Deborah Lee James announced late last month that the service is reviewing the company's schedule for the tanker to ensure it is on track to meet deadlines.

Adding to Boeing's troubles, service officials warned this month that the Air Force may be forced to break the KC-46 contract if the Pentagon is slapped with a yearlong continuing resolution (CR) at the beginning of the fiscal year.

If Congress can not come to a budget agreement by Oct. 1, the Pentagon may be forced to operate under a long-term CR, a stop-gap spending measure that temporarily funds the government at prior year levels.

The KC-46 contract with Boeing requires the Air Force to award eight aircraft at minimum in the second low-rate initial production lot planned for fiscal year 2016. But in fiscal 2015, the Air Force only budgeted for seven aircraft in LRIP 1. If the service is only allowed to buy seven aircraft in fiscal 2016 due to a yearlong CR, that would breach the terms of the contract, according to Richardson.

Lt. Gen. Arnie Bunch, the service's deputy assistant secretary for acquisition, said this week that the Air Force would likely seek an exemption from the CR for KC-46. However, leadership expects the CR to affect about 50 programs across the Air Force, including the F-35 fighter jet. The Air Force has only so much negotiating power with Congress, and must balance among its priorities.

Twitter: @laraseligman