A government report in 2024 revealed that air traffic control technology is outdated, replacement parts are hard to get, and technicians who can service key equipment have retired. 

On Jan. 11, 2023, the Federal Aviation Administration grounded flights across the nation after an unexpected outage to the Notice to Air Missions system (NOTAM), sparking a government investigation. NOTAMs notify pilots during flights about changes to airspace, airports, and equipment. 

The report from the Government Accountability Office found that the FAA has trouble with upkeep on its equipment, which needs modernization, while airspace demand has seen dramatic growth since the introduction of those systems.

“Specifically, according to the FAA officials, aging systems have been difficult to maintain due to the unavailability of parts and retirement of technicians with expertise in maintaining the aging systems,” the report said. 

It found that 37% of the FAA’s 138 air traffic control systems were deemed unsustainable, meaning replacements come sparingly and there is a significant lack of funding available to modernize the technology.

For example, the Airport Surface Detection Equipment Model-X, which debuted in the early 2000s, tracks movement on the runway. But spare parts for this device are “extremely limited and may require expensive special engineering.”

Additionally, beacon replacement antennas are no longer available as they are on average two decades old. And 25-year-old landing systems used to help aircraft on its final approach now lack manufacturing support.

The report also highlighted several unnamed systems critical to safety and operations that are 20 to 30 years old, with some up to 50 years old. Timetables for reinvestment in the systems won’t occur until 2030 at the earliest, if at all. 

According to the report, the FAA did not use risk assessment to prioritize or establish short-term plans to modernize systems lacking a timeline.

In the Transportation Department’s reply to the investigation, it agreed that reinvestment in its airspace systems is a top priority. 

“The FAA has taken significant actions to identify and implement system upgrades and modernization,” Philip A. McNamara, then-Transportation assistant secretary for administration, said in the response letter. 

Additionally, more than 90% of the nation’s air traffic control facilities fall below the FAA’s recommended staffing levels, The New York Times reported.  

National Air Traffic Controllers Association President Nick Daniels said in an interview with CBS News that there are 10,800 air traffic controllers, but it should be 14,335.

“We have a controller shortage in this nation,” he warned.

Accident investigators are still sorting through the details to determine the cause of the midair collision of a passenger plane and an Army helicopter near Washington, DC, on Wednesday night. But the shortage of controllers has come under scrutiny.

An FAA report obtained by the Associated Press revealed that one person at air traffic control at Reagan National Airport was doing the work of two people at the time of the crash.

“It is not uncommon for us to combine positions, routinely combine positions, decombine positions,” Daniels said.

Fortune has contacted the FAA but hasn’t received a comment yet.