WASHINGTON — The U.S. Air Force has officially abandoned a directive to get its F-35, F-22 and F-16 jets up to an 80 percent mission-capable rate after failing to meet that goal in fiscal 2019, the service’s presumptive chief of staff indicated Thursday.

According to written responses by Air Force Gen. Charles Q. Brown ahead of his May 7 confirmation hearing, “the F-16 mission capable rate reached a high of 75% in June 2019, the F-22 mission capable rate achieved a high of 68% in April 2019 and the F-35 mission capability rate climbed to a high of 74% in September 2019.”

However, data obtained exclusively by Air Force Times and Defense News revealed the mission-capable rates for those three aircraft over the whole of FY19 — while, in some cases, an improvement over the previous year — fell well short of the 80 percent goal mandated by then-Defense Secretary Jim Mattis in October 2018.

And the overall rates for the year were lower — in some cases, much lower — than the high-water marks cited by Brown.

The Air Force’s newest fighter jet, the F-35A conventional-takeoff-and-landing model, showed the most improvement, increasing from a mission-capable rate of about 50 percent in FY18 to 62 percent in FY19.

The F-16 mission-capable rate grew modestly, with the F-16C increasing from 70 percent in FY18 to 73 percent in FY19. The F-16D’s mission-capable rate rose from 66 percent to 70 percent over that time period.

However, the F-22’s mission-capable rate actually decreased from 52 percent in FY18 to 51 percent in FY19. This is likely due to the continued maintenance challenges after 17 Raptors were left behind at Tyndall Air Force Base, Florida, during Hurricane Michael in 2018, damaging a portion of the fleet.

Ultimately, Pentagon leadership decided not to renew the effort in FY20, Brown told the Senate Armed Services Committee.

“The Office of the Secretary of Defense determined the FY19 80-percent Mission Capable (MC) Rate initiative is not an FY20 requirement,” wrote Brown, who is currently the commander of Pacific Air Forces.

Instead, the Air Force has returned to its usual practice of letting commanders set their own readiness objectives, with no definitive requirements for mission-capable rates, he said.

“We continue to balance near term readiness recovery with investment long-term combat capability,” Brown said. “While maintaining all of our aging fleets are difficult and expensive, we continuously examine emerging technologies, commercial best practices, and other methods to reduce the sustainment costs for our Air Force.”

Although the services tried to meet Mattis’ 80 percent mandate, even after he resigned in December 2018, the goal was never popular among Air Force leadership.

If confirmed by the Senate as the uniformed head of the Air Force, Brown will replace Gen. Dave Goldfein, who argued that the readiness of the service’s aircraft inventory could better be measured by other metrics.

In an interview with Air Force Times in August, Goldfein said readiness can truly be measured by how well the Air Force can carry out its missions, which requires more than mission-capable aircraft. It also requires trained and ready air crew, maintainers and other airmen as well as enough spare parts and resources, he said. Goldfein also cited increases in flying hours and pilot training as other indicators of progress.

Instead of driving toward an 80 percent mission-capable rate, the Air Force is implementing a new “strategic sustainment framework” that will aim to increase readiness by improving the service’s repair network and expanding the use of conditions-based maintenance, Brown wrote in his response to the SASC.

The service’s inspector general is also conducting a comprehensive classified review of readiness assessments across the Air Force, he said.

In his hearing, Brown reiterated the Air Force’s need to grow to 386 squadrons over the long term. When asked by Sen. Deb Fischer, R-Neb., whether the Air Force is now large enough to carry out the National Defense Strategy, Brown said: “To an extent.”

“In the immediate term, I think we are, but we’ve still got to be able to grow to the 386” squadrons, Brown said. “Anything less than 386 incurs risk.”

However, he acknowledged the Air Force may come close but might not completely meet that goal, which was first laid out by previous Air Force Secretary Heather Wilson. But the Air Force’s improved capabilities, including making better use of unmanned platforms, will help make up some of that difference, he said.

“We may be a little bit smaller than 386, but we’ll be more capable,” Brown said. “It’s not just the manned platforms; it’s also how we do manned-unmanned teaming. The XQ-58 Valkyrie [combat drone] is one of those systems that we can team up with, particularly some of our fifth-gen capability to increase our range, increase our awareness, to increase our strike capability.”