American has cancelled 282 flights—9% of its schedule—according to flight-tracking service FlightAware. Spirit has called 290, a whopping 42% of its scheduled flights today.

While severe weather was a major contributor, CNBC reports at least 120 of American’s cancelations were due to the lack of a flight crew.

Sunday’s storms caused nearly 2,000 flight delays and hundreds of cancellations. That backlog rolled into Monday as well, with another 445 outward bound flights being delayed, and 409 incoming flights not arriving on time. Nearly 500 flights were canceled as well. American, systemwide, was forced to cancel 563 flights and Spirit cancelled 334.

Passengers, understandably, are not happy about today’s cancellations and are taking to social media to address what they call poor communication from the carriers.

Spirit, in a Tweet, told customers, “We are experiencing operational challenges in some areas of our network. Before going to the airport, check your email and current flight status.”

American could do without the PR headache of the cancelled flights, as it’s also dealing with the fallout of a fistfight between two passengers on a Sunday flight that was recorded and has since gone viral.

Despite the rise of the Delta variant, more and more people are taking to the skies once again, following nearly a year and a half of stay-at-home orders. The Transportation Security Administration screened 2.24 million people on Sunday. That’s the most since Feb. 28, 2020.

Carriers, though, are still staffing up, leaving little wiggle room when there are substantial delays. The Federal Aviation Administration mandates pilots and crews rest for a certain length of time before they’re able to work.