The Federal Aviation Administration said late Sunday, Oct. 19 that air traffic control staffing issues were delaying travel at airports in Dallas, Chicago, Atlanta and Newark as a U.S. government shutdown became the third-longest in history.

It's not clear, however, if the issues are tied directly to the shutdown.

The FAA has had long-standing staffing issues, and air traffic controllers routinely had to work significant overtime, even before the shutdown began.

According to Cirium, an aviation data analytics company, more than 82% of flights departed on time in the U.S. in the first 17 days of the shutdown. Cirium's press release said that is average to above-average performance for the national airspace.

More: Is it safe to fly during the government shutdown? What you should know.