Marine aviation squadrons are suffering more than ground units after 15 years of war and deep budget cuts, Commandant Gen. Robert Neller told lawmakers on Tuesday.

“We would — as a goal — like to have 80 percent of our units ready to go,” Neller said at House Appropriations Defense Subcommittee hearing. “We’re not quite there, particularly on the aviation side.”

Readiness levels for ground units are “trending up,” Neller said.

“The Congress has given us $5 billion to reset our ground equipment,” he said. “We’ve got about 79 percent of that complete — and about 50 percent of that equipment is back to the force.”

Aviation is “a little different story,” due to the delays in the F-35 program, budget cuts and other issues, Neller said.

“Our aviation readiness is really my No. 1 concern,” he said. “We don’t have enough airplanes that we would call ‘ready basic aircraft.’ That means we’re not getting enough flight hours.”

The readiness issues that Marine Corps aviation units have been caused by a variety of factors, so there is no single solution, Neller told reporters after Tuesday’s briefing.

Marine Corps Commandant considers extending time between deployments, says transgender troops remain 'until we hear otherwise'

Read Next: Marine Corps Commandant considers extending time between deployments, says transgender troops remain 'until we hear otherwise'

“We’ve been an operating at a high rate,” Neller said. “Sequestration affected the work force at some of the fleet readiness centers. There are some parts issues with new airplanes. We’re in the middle of fielding brand new model type series for every plane right now except for CH-53s. We left our airplanes overseas — particularly our rotary wing — probably longer than we should have, looking back it.”

Neller also stressed that the Marine Corps needs to get new aircraft, such as the MV-22B Osprey and F-35B.

“We’re — I think — 281 of 360 on Ospreys and we’re still at the beginning of the F-35 that is going to replace three airframes,” he said. “We’re in pretty good shape on the Hueys and we’re a little bit slower on the Cobras.”

Read more at The Marine Corps Times