Travelers at DFW International Airport are feeling the effects of flight delays caused by FAA staffing shortages amid ongoing government shutdown.

As the country’s second-longest government shutdown hits day 27, air traffic controllers are calling in sick and “wearing thin”—leading to flight delays in major U.S. hubs.

Flights to DFW International Airport are delayed about 18 minutes, according to the Federal Aviation Administration.

Staffing issues are causing delays for incoming flights at DFW International Airport, according to an alert from the Federal Aviation Administration on Monday.

A maintenance issue delayed about 1,000 American Airlines flights in the United States on Wednesday. That included more than 400 delays and about 40 cancellations at Dallas-Fort Worth International Airport, according to the flight-tracking website FlightAware.

All incoming flights at Dallas-Fort Worth International Airport are delayed due to staffing issues, according to an alert sent by the Federal Aviation Administration. The FAA posted the alert for a ground delay at DFW Airport around 1:30 p.m. on Monday, Oct. 27. The delay is expected to last until 10 p.m.

The FAA is preparing for more possible ground stops and delays at several major airports amid air traffic controller shortages in the government shutdown.