The Federal Aviation Administration doesn’t have enough air traffic controllers to control the nation’s air traffic. It’s a big problem. Airlines have been forced to delay, reschedule or cancel thousands of flights, especially at Newark Liberty International Airport in New Jersey. If you’ve flown recently, perhaps you’ve had some extra time on the tarmac to wonder what went wrong.

A big part of the answer: Government shutdowns.

Repeated disruptions to the F.A.A.’s funding over the last 15 years, caused by shutdowns and other budget fights, have played a key role in preventing the agency from hiring and training enough controllers. As Congress lurches and sways toward another potential shutdown, the F.A.A.’s travails illustrate the stakes.

Shutdowns tend to be brief, because Americans are soon reminded that the government does important things. But the end of a shutdown doesn’t mean that everything springs back to normal. Some of the damage endures. A government shutdown in 2013 wiped out the annual research season for the U.S. Antarctic Program, causing more than two dozen scientific studies to lose a year of data. Another shutdown, beginning in December 2018, forced the cancellation of about 86,000 immigration court hearings, some of which took years to reschedule. During that shutdown, unsupervised tourists cut down Joshua trees in Joshua Tree National Park. The slow-growing trees can take 50 years to reach full height.

The funding disruptions are particularly difficult for the F.A.A. It takes years to train air traffic controllers, and there are limits on how many can be trained at one time. When the pipeline isn’t fed, the agency falls behind — and you end up stuck in the wrong city.

The F.A.A.’s struggles are anatomized in a recent report by the National Academies of Sciences, Engineering and Medicine, which convened a panel of experts to examine why the agency was having such a hard time putting bodies in air traffic control towers.

In the early 2010s, every federal agency was preparing for a large cohort of baby boomers to walk into retirement. The F.A.A.’s challenge was particularly acute because it had hired many of its controllers around the same time, as replacements for the strikers fired by President Ronald Reagan in August 1981.