Travelers across the country faced the possibility of canceled or delayed flights on Saturday as airlines and airports dealt with a combination of high demand and bad weather.

As of late Saturday afternoon, more than 600 flights in the United States had been canceled and nearly 4,000 flights within or out of the country had been delayed.

There were more problem flights than on a typical travel day. The number of travelers over the Fourth of July holiday weekend had reachedprepandemic levels according to the transportation security administration. Demand for travel over the same holiday weekend last year was much higher than it is this year.

Dallas-Fort Worth International Airport, O'Hare International Airport in Chicago and Charlotte Douglas International Airport in North Carolina were the three airports that had the most delays and canceled flights on Saturday.

Over the Christmas and New Year's holidays, when bad weather and Omicron shortages wreaked havoc with airline schedules, the number of canceled and delayed flights was much higher.

As they struggle with a pilot shortage, the airlines are scrambling to keep up with demand this July 4 holiday.

Delta teams continue to manage through the compounding factors of weather and air traffic control delays, which impact available flight crew duty time, according to a Delta Air Lines spokesman. We apologize to our customers for any disruption to their travel plans because canceling a flight is our last resort.

If customers are traveling between the same origin and destination, Delta will allow them to change their flights without changing their fares.

The airline blamed weather and air traffic control programs.

Adding to the stress at American Airlines was a computer glitch that allowed some trip trading that shouldn't have been allowed. The primary drivers of delays/cancellations on Saturday were weather and traffic control issues, according to American.

The FAA said weather conditions and travel demand were the main causes of flight delays and cancellation. The F.A.A has acted on issues raised by airlines and is working with them to share information to keep aircraft moving safely. The agency has put more controllers in high demand areas and added alternate routes.