NEWARK, N.J. () With the federal government shutdown in its second week, shortages of air traffic controllers have strained operations and disrupted flights at some U.S. airports.

The Federal Aviation Administration said staffing issues were resulting in delays at airports including Phoenix, Newark and New York’s LaGuardia with more expected later in the day.

More than 2,500 flights have been delayed by 1 p.m. ET Friday, after 22,000 had been delayed since Monday. Air travel is expected to rise in the United States during the three-day Columbus Day holiday weekend.

Earlier, the head of the FAA said that the agency is facing continuing air traffic control staffing shortages as a U.S. government shutdown entered its 10th day but emphasized safety would not be compromised.

“Staffing shortages have increased across the country,” FAA Administrator Bryan Bedford said in an email to employees. “Safety will never be compromised. When staffing constraints occur, we will reduce the flow of air traffic into affected airports and centers to maintain safe operations.”

About 13,000 air traffic controllers and approximately 50,000 Transportation Security Administration officers must still turn up for work during the government shutdown, but they are not being paid.

Reuters contributed to this report.