Air travel complaints were up nearly 35% in June compared to the month before, according to a report from the Department of Transportation released Friday. Nearly one-third of those complaints were about airline cancellations, delays and other schedule changes.
DOT data shows that 583,584 flights were operated in June, which is down about 1% from flights operated during May. Airlines reported that 73.5% of scheduled flights were on time in June of 2022, which is actually higher than the pre-pandemic on-time data which was 73.3% in June of 2019.
The data showed that 3.1% of airlines' domestic flights were canceled which is almost double the 1.6% of flights canceled in June 2021.
Some airlines had fewer scheduling problems than others, according to the data.
The most on-time airlines in June were Alaska Airlines, with nearly 79% of flights arriving on time, Delta Air Lines and Hawaiian Airlines. The airlines with the lowest on-time arrivals were Allegiant Air, with only 59% of flights arriving on time, JetBlue Airways and Frontier Airlines.
Hawaiian Airlines had the lowest rate of canceled flights, with only .1% of flights canceled. Alaska Airlines and Frontier Airlines also had a low rate of cancellations, with .7% and 1.1% canceled respectively.
American Airlines reported the highest rate of canceled flights in June, with the carrier canceling 4.4% of scheduled flights, according to the data. Delta Air Lines and United Airlines also had a higher rate of cancellations, with 3.9% and 3.5% of flights canceled respectively.
About a quarter of the complaints regarded refunds from airlines. DOT said that their office has investigated 10 airlines for failing to refund "extreme delays," and hints that there are ongoing investigations into more airlines.
"Many passengers who were initially denied refunds have since received the required refunds," the report said. "The Department has taken and will take enforcement action against noncompliant airlines and ticket agents as necessary. [Office of Aviation Consumer Protection] recently concluded its investigation of 10 airlines and is pursuing enforcement action against them for extreme delays in providing refunds for flights the airlines canceled or significantly changed."
The report added, "The Office is also actively investigating the refund practices of additional airlines flying to, from, or within the United States."
The data also showed small increases in mishandled baggage, wheelchairs and scooters in June, compared to the previous month.
This report comes after Transportation Secretary Pete Buttigieg sent a letter to air carriers last week, calling on them to shape up ahead of the Labor Day travel weekend.
"In the first six months of 2022, roughly 24% of the domestic flights of U.S. airlines have been delayed and 3.2% have been canceled," Buttigieg said in the letter. "As you know, these aren’t just numbers, these are missed birthday parties, graduations, time with loved ones and important meetings."
ABC News' Sam Sweeney contributed to this report.