The Federal Aviation Association (FAA) handles nearly 70,000 flights a day, and at any given moment there are 7,000 planes zooming through the clouds above. Air traffic controllers (ATC) keep order in the sky, but recent statistics show turbulence in the FAA’s ability to hire enough to keep airports running smoothly into the future.

According to National Air Traffic Controllers Association (NATCA), the FAA has missed hiring goals for seven consecutive years. NATCA President Paul Rinaldi has gone so far as to say that the hiring shortage has reached crisis level, with the number of fully certified ATCs falling to a 27-year low.

That’s likely why the FAA has made a recent push to bring in new recruits. On Sept. 7, the FAA opened a vacancy announcement, seeking candidates with 52 weeks of full-time air traffic control experience in addition to other certifications and ratings. Applications are due by Sept. 20, 2016. The FAA also sent out a call for entry-level air traffic control candidates on Aug. 2. By the time the application window closed on Aug. 15, the FAA had received more than 29,000 applications.

“Although NATCA does not believe that the safety of the air traffic control system is at risk, without proper staffing at our facilities, efficiency and modernization efforts are being negatively affected,” said Rinaldi in a press release. “This could lead to further system inefficiencies, delays, and a reduction in air traffic services for the flying public.”

So why doesn’t the FAA just hire a bunch of air traffic controllers? Easier said than done. There are currently 14,000 certified ATCs in the US, but it’s estimated that only 2% or 3% that group has the right personality and aptitude to be successful at the job.

An air traffic controller “should have a super short-term memory so that he or she can deal with what is in front of them and disregard no longer relevant information,” says Tammy Jones from the FAA communications office. “They need to be fast, real-time thinkers – able to process visual and audio information simultaneously from multiple sources.”

To become an air traffic controller, applicants must be a US citizen, speak English clearly and be under the age of 31. The age requirement is so low because the mandatory retirement age is 56. Most air traffic controllers average 20 years of service.

Last month, the FAA announced it was teaming up with SureSelect, an ATC-specific-recruitment and pre-screening assessment. The personality and aptitude test was given to 2,000 candidates, and an FAA study shows that those who performed well went on to be successful air traffic controllers.

“It is one of the most stressful positions in the world, and personality testing is all about fit,” said Greg Ford, psychologist and CEO of TalentClick, a personality testing company. “There is no wrong personality, but some people are a better fit based on their hard wiring.”

Being an air traffic controller is serious, stressful, and has zero margin for error, so passing the assessment isn’t a silver bullet. Once accepted, trainees must undergo qualification training at the FAA academy in Oklahoma City, Okla., where they gain air traffic control knowledge through classroom and simulation training while making a salary of $18,343 a year.

Initial training can take up to five months, after which trainees move on to more advanced training and ultimately, two or three years of on-the-job training. The FAA spends about $480 million to train ATC’s every year, but nearly $143 million is spent on trainees who fail to quality or complete the program.

Those who do make it through the training can expect to make about $38,000 during their initial assignment. The pay range for Certified Professional Controllers varies within a pay range from $49,666 to $144,195 a year, based on the level of the facility, employees’ experience and other factors.

The FAA says there was a dip in hiring after the 2013 government shutdown and budget cuts, which curtailed controller hiring and training at the FAA academy — delaying initial training for several classes of new ATCs. Still, they’re confident their numbers will rise in the near future, and they plan to hire 1,781 new controllers over the next year and 6,836 over the next 5 years

“The agency has been working hard to hire at an increased rate to meet its air traffic controller staffing targets,” said Jones. “We are on track to meet our hiring goals.”

Brittany is a writer at Yahoo Finance.

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