An air travel boom appears to be in full swing, but over the weekend and into Monday it was accompanied by familiar pre-pandemic frustrations: Flight delays and cancellations for those traveling on American and Spirit airlines.

On Sunday, 341 — or 40 percent — of Spirit Airlines’ flights were delayed with about 165 canceled, according to the flight-tracking website FlightAware.com. About 30 percent — or 948 — of American’s flights were delayed with 238 canceled, the website reported. Southwest Airlines also had a significant number of delays Sunday, according to FlightAware, with about 42 percent of flights delayed.

Monday was equally frustrating as airlines struggled to catch up.

FlightAware reported delays for 23 percent of Spirit’s flights and cancellations for 36 percent of them. About 25 percent of American’s flights were delayed and 15 percent were canceled. About 26 percent of Southwest’s flights were delayed, according to FlightAware.

American Airlines blamed storms in Texas for the delays and cancellations.

“We have experienced cancellations and delays yesterday and today, mainly due to weather and ATC impacts at DFW Airport, including two ramp closures yesterday and a ground stop earlier today related to ongoing weather-recovery efforts,” the airline said via email. Airline officials said they expected issues to clear up by Tuesday.

Spirit Airlines also blamed weather and other unspecified “operational issues.”

“We’re working around the clock to get back on track in the wake of some travel disruptions over the weekend due to a series of weather and operational challenges,” said spokesman Field Sutton. “We needed to make proactive cancellations to some flights across the network, but the majority of flights are still scheduled as planned.”

The Association of Flight Attendants-CWA, which represents Spirit’s flight attendants, quickly knocked down reports that the airline’s issues were due to a strike.

“Spirit Airlines is experiencing operational issues causing flight delays and cancellations due to weather, schedule month change over, and IT outages,” the union said in a emailed statement. “A few news outlets have incorrectly reported that this may be due to a strike. This is not true.”

The delays and cancellations came as the Transportation Security Administration reported setting a record for the number of passengers screened Sunday. TSA said 2,238,462 million people moved through airport security checkpoints, topping the previous record set July 18.