Travelers wait in line to check-in at John Wayne Airport in Santa Ana, California on Wednesday, June 30, 2021.

Paul Bersebach | MediaNews Group | Orange County Register via Getty Images

Air travelers’ complaints to the federal government rose almost 18% in June from a month earlier, as flight cancellations and other disruptions increased, the Ministry of Transport said on Friday.

In June, DOT received 4,176 complaints about air traffic, more than 55% of which concerned reimbursements. It also received a compliment but didn’t immediately say which airline or topic it was about.

Airlines faced staff shortages this summer due to an increase in air travel demand that exceeded their expectations. At the start of the pandemic, airlines urged thousands of employees to retire or retire to save costs.

Ten U.S. airlines canceled 1.6% of the 573,779 domestic flights they had scheduled in June, almost four times as many as in May, the DOT said. The punctuality rate fell from 86.2% in the previous month to 74.6%.

Hawaiian Airlines, Delta Air Lines and Alaska Airlines had the best punctuality rates in June at 87.7%, 86.8% and 80.7%, respectively. Allegiant Air had the lowest on-time arrival rate of the 10 airlines at 56.6%, followed by Southwest Airlines at 62.4% and JetBlue Airways at 65.1%.

American Airlines ranked fourth for on-time arrivals with 74.3%, Spirit Airlines with 74.1%, United Airlines with 73.9% and Frontier Airlines with 69.5%.

Dallas-based Southwest had two technical outages in June that contributed to flight cancellations and delays.

The DOT data doesn’t cover the late July and early August meltdown at Spirit after the airline canceled more than 2,800 flights due to bad weather, technology issues and staff shortages. American also canceled hundreds of flights in early August after bad weather at the Dallas / Fort Worth International Airport hub combined with staffing shortages.

Earlier this week, American announced it had suspended plans to shut down a pilot training center in Charlotte, North Carolina, as more pilots are needed to meet rising travel demand.