Tensions for travelers are rising this holiday weekend as cancellations and delays abound in airports across the country. ABC reports that the union for American Airlines said a computer glitch might leave at least 12,000 flights may be without pilots throughout July. Pilots were offered double pay to make up for a similar incident in 2017, but no offer has been made yet.

Almost 600 Friday flights were canceled and over 7,600 were late, CNBC reports. The disruptions eased to about 700 delayed flights by this morning. Close to 30 percent of American Airlines’ entire schedule was delayed Friday—970 flights—and Delta wasn’t too far behind, with 756 flights delayed, about a quarter of its schedule. Amid airline staff shortages and widespread protests, flight problems are higher than pre-pandemic numbers.

“If you’ve encountered delays and cancellations recently, I apologize,” Delta CEO Ed Bastian wrote in an email frequent flyer members Thursday. “This level of disruption and uncertainty is unacceptable.” Transportation Secretary Pete Buttigieg tweeted today that travelers should apply for a refund if their flights are canceled.