At the end of 2016, the Marine Corps had 1,065 aircraft on flight lines around the world, ranging from small attack helicopters to C-130 transport planes.

Of those, only 439 are considered ready to fly as is. The remaining aircraft, nearly 60 percent of the total, are considered temporarily non-mission capable, either awaiting maintenance, in-service repair or supply, meaning they are lacking the parts they need to be operational.

And as the Corps works to claw back readiness and increase pilot flight hours from postwar lows in 2014, it's the spare parts issue that has the service's top aviator most concerned.

Speaking to reporters this week, Lt. Gen. Jon "Dog" Davis, deputy commandant for aviation, said aircraft maintainers are still sometimes resorting to cannibalization, or borrowing parts from working aircraft to make other planes operational.

He made his concern clear in a wish list to Congress that each service recently submitted in anticipation of a forthcoming supplemental defense budget for this year.

"On my unfunded priority list, one of the biggest things we've been banging the drum about is the need to refill our coffers on our supply parts," he said. "It's a big problem both for the new airplanes and the old ones."

Among the Marine Corps' most used fighters, rotorcraft and transports, the problem is universal. Of aircraft that are in-reporting but can't fly, the percentage of those down for parts is as follows, Davis said:

For the Hornet, which has been particularly troubled by readiness issues, 29 percent of all 171 aircraft in reporting are down for supply, Davis said.

"The one thing that is holding the man down on every platform is not-mission-capable supply," Davis said. "By every type/model/series, it's a contributor to why that airplane might not be available for flying."

The Corps is still about 150 aircraft shy of the number of ready basic aircraft it needs to allow all aviators to meet their flight hour goals, a key requirement for both proficiency and safety.

The Marine Corps Hornet community, which sustained seven crashes in the last fifteen months with three pilot fatalities, is about 20 aircraft shy of what it needs to make flight hour goals, with 72 ready basic aircraft out of the 171 in reporting, Davis said.

While the aircraft readiness crisis has had minimal impact on deployments and forward operations up until now, the Corps did recently pull half its MV-22 Ospreys back from its forward-deployed crisis response task force for Africa, reducing the presence in theater from 12 aircraft to six.

"We couldn't sustain them," Assistant Commandant Gen. Glenn Walters told lawmakers in a hearing this week. "The requirement was still there, but we couldn't sustain it."

Davis said the Marine Corps is on track to make pilot flight hour goals by 2019. It will be the first time the service has hit that marker since 2012.

"If I'm a businessman, I'm underwater right now, because I don't have enough power tools to make my flight hour goal," he said.

-- Hope Hodge Seck can be reached at hope.seck@military.com. Follow her on Twitter at@HopeSeck.