The US Navy lacks the parts and materials it needs to keep hundreds of fighter jets operational, which could affect the nation’s ability to fight future wars. That’s the key takeaway from an audit released this week (pdf) by the Department of Defense Inspector General (DODIG), which is focused on the Boeing F/A-18E/F Super Hornet—the Navy’s workhorse attack aircraft since 1995.

“Although Navy and DLA (Defense Logistics Agency) officials identified the quantity of spare parts needed, the officials could not obtain the quantity needed to satisfy current demand and fill backorders,” reads the partially redacted audit, in the works since March 2018. Because of this, the Navy “may not meet sudden increases in operational mission readiness requirements or the Secretary of Defense’s goal of 80‑percent mission capable rate for the Super Hornet fleet by the end of FY 2019.”

About half of the Navy’s 546 Super Hornets were operational as of last year.

A lack of spare parts has been a problem for the service, and the “readiness problems” remain largely unsolved. To meet its immediate requirements, the Navy has been cannibalizing parts for the Super Hornet from other planes, a situation the inspector general calls unsustainable. At a congressional hearing a few years back, Rep. Mac Thornberry, a Texas Republican, spoke of the Marine Corps having to cannibalize F/A-18 parts from a model on display at a museum in order to get current aircraft ready to fly. Both the Navy and US Air Force were called out last year by the Government Accountability Office for not having met “aircraft availability goals.” And according to a 2017 DLA report, spare parts for the Navy’s AV-8B Harrier II engines, manufactured by Rolls-Royce, had not been delivered on schedule. As a result, the Navy “scavenged parts from mission-ready engines, decreasing the inventory and number” of usable planes.

“The business of the Pentagon is not actually fighting and winning the nation’s wars, it is spending vast sums of taxpayer money buying big, expensive glitzy hardware,” Dan Grazier, a military analyst at the nonpartisan Project on Government Oversight, told Quartz. “And so that almost always takes priority over maintaining the older stuff.”

Grazier, who served as a captain in the US Marine Corps, said the Navy has invested tens of billions of dollars developing new, unproven systems while proven systems like the Super Hornet can’t get all the parts they need to keep operating. He pointed to the DDG-1000 Zumwalt-class destroyer, a defect-riddled money pit that was canceled by the Navy after just three were built, as one example. Another, the Navy’s highly anticipated Littoral Combat Ship, has been called a “complete failure.” That program, which has also been curtailed, cost the Navy some $30 billion.

But the program perhaps most directly connected to the Navy’s current spare parts problem is the F-35, said Grazier. The military’s next-gen fighter jet is its most expensive ever, yet has suffered from delays, cost overruns, and underperformance. The Navy canceled various contracts to continue purchasing spare parts for the Super Hornet in the late 1990s and early 2000s, expecting to have an operational F-35 in the 2010-2012 timeframe. That, of course, hasn’t happened.

“The plan and the promises that were made about the F-35, its capabilities and its original cost estimates were wildly wrong and hugely unrealistic,” said Grazier. “They’re now suffering the consequences of that because the F-35 still isn’t ready to go.”

If the Navy had performed the required logistics assessments between 2000 and 2018, it would have been able to forecast the current situation and plan for it, says the DODIG report.

There are five crucial parts the Navy needs to maintain the operational readiness of the F/A-18 E/F Super Hornet fleet, the report explains: the plane’s electrical generator; its center cockpit display; the primary targeting sensor; the communications antenna; and the tail rudder actuator. They are each currently back-ordered; the precise length of the delays are redacted in the publicly released version of the report.

Specific causes include: obsolete materials that are no longer made or available for purchase; manufacturing and delivery delays; and a quirk in certain Defense Department contracts that forbid the Navy from producing its own parts or fixing the ones they already have.

The Super Hornet’s center cockpit display is made with a type of glass that is now obsolete, according to the report. At the end of 2018, the contractor responsible for it had just 68 pieces left. A Navy official told IG investigators that the service was “working on approving a new type of glass” for the display units. The timeline for this is redacted in the report.

The Super Hornet’s most back-ordered component is the plane’s communication antenna, due to production delays. A DLA official told the inspector general that only one vendor is capable of manufacturing the part. However, this particular contractor moved from Massachusetts to Pennsylvania “and experienced delays getting the production line running,” making it impossible to get new ones for a 13-month period.

An even more pedestrian issue prevented the Navy from repairing the Super Hornet’s rudder actuators, says the report: “[T]he Fleet Readiness Center’s Southwest facility did not have enough operational test benches to handle the demand for required quality tests and certification of repaired spare parts.”

The report points out that Boeing, the Super Hornet’s manufacturer, was for some reason unable to provide spare communication antennas for the aircraft. The Navy could, conceivably, build replacements by itself, but the government does “not own the technical drawings for the part. Therefore, the DLA could not acquire the communication antenna from anyone other than the sole‑source manufacturer.”

Having the necessary data, build sheets, and so forth would further allow the Navy to find other vendors willing to make the components. However, the cost of acquiring the intellectual property rights to the data was “prohibitive,” says the report.

“Defense contractors want to be able to maintain control of their products, because where they make their real money is on the back-end, after we purchase it, in long-term sustainment contracts,” explained Grazier. “The issue of intellectual property rights is a really, really big deal. It sounds really mundane, but it has enormous consequences to the military.”

When a defense contractor retains the intellectual property rights to something like a fighter jet, it becomes the only firm that can perform long-term sustainment and maintenance for the aircraft.

“The only way that you can upgrade the aircraft, the only way that you can handle a lot of the basic maintenance functions of it, is having access to all that data,” Grazier continued. “And so the government can’t go out and do a competitive bid each year for the sustainment of a system, because only one firm has the necessary information. It means that [defense contractors] have the American people over a barrel. They can basically charge whatever they want for the sustainment contracts because there’s nowhere else that we can go to get the services done.”

In a response to the DODIG report, the Navy says it is taking steps to rectify the spare parts situation plaguing the Super Hornet.

“It’s definitely an issue,” said Grazier. “And it’s one that the service needs to address sooner rather than later.