WASHINGTON — Boeing’s first F-15EX took to the skies for its inaugural flight on Feb. 2, a milestone that will allow the company to deliver the first two planes to the U.S. Air Force by the end of March.

After a couple of hours of delays due to weather — which also held up plans to conduct a first flight on Feb. 1 — Boeing test pilot Matt “Phat” Giese took off from Lambert International Airport in St. Louis, Missouri, at approximately 1:57 p.m. EST.

The flight lasted approximately 90 minutes, and the plane performed as expected, Boeing said in a news release.

“Today’s successful flight proves the jet’s safety and readiness to join our nation’s fighter fleet,” said Prat Kumar, Boeing vice president and F-15 program manager. “Our workforce is excited to build a modern fighter aircraft for the U.S. Air Force. Our customer can feel confident in its decision to invest in this platform that is capable of incorporating the latest advanced battle management systems, sensors and weapons due to the jet’s digital airframe design and open mission systems architecture.”

The Air Force first added the F-15EX to its fiscal 2020 budget at the behest of the Defense Department’s Cost Assessment and Program Evaluation office, or CAPE.

With the Air Force and Air National Guard’s fleet of 1970s-era F-15C/D jets showing signs of age, the service needed to either conduct an expensive life extension or buy new planes to replace them.

But with F-35 operations and sustainment costs still financially burdensome, CAPE officials argued that buying an upgraded version of the F-15E Strike Eagle — with new features developed primarily at the cost of foreign customers like Qatar and Saudi Arabia — would be a more cost-conscious option.

The Air Force placed its first order for the F-15EX in July 2020, awarding a contract for the first lot of eight jets with a value not to exceed about $1.2 billion. The entire program has a ceiling value of $23 billion.

The new jets come with a host of modern features, including Honeywell’s ADCP-II mission computer, the Eagle Passive/Active Warning and Survivability System electronic warfare system made by BAE Systems, the Raytheon Technologies’ AN/APG-82 radar, fly-by-wire flight controls, and a digital cockpit.

The service expects to buy at least 144 F-15EX aircraft, but the contract includes options to allow the Air Force to purchase up to 200 jets.

Congress first included funds in December to purchase eight F-15EXs through the fiscal 2020 spending bill, and lawmakers approved spending $1.2 billion to buy 12 F-15EXs in fiscal 2021. According to the Air Force’s FY21 budget request, the service plans to buy another dozen planes in FY22, procuring 14 F-15EXs in FY23, and ramping up to 19 jets per year in both FY24 and FY25.

Once delivered to the Air Force, the first two F-15EXs will go Eglin Air Force Base, Florida, for testing, with the remaining six aircraft set to be delivered to the base in FY23.