By David Shepardson

WASHINGTON (Reuters) -The U.S. aviation system is expected to “remain challenged this summer and beyond” and the Federal Aviation Administration (FAA) needs more air traffic control staff, a senior United Airlines executive said on Wednesday.

The FAA responded to United Wednesday, saying on July 3 and 4 “there were no FAA staffing-related delays at all, yet airlines still canceled over 1,100 flights, a quarter of which were United Airlines flights.”

Summer travelers face mounting flight cancellations as demand rises and the industry tries to rebuild staff levels after thousands of workers left during the COVID-19 pandemic.

“The reality is that there are just more flights scheduled industrywide than the (air traffic control) staffing system can handle,” United’s chief operations officer, Jon Roitman, said in a message to staff seen by Reuters.

“Until that is resolved, we expect the U.S. aviation system will remain challenged this summer and beyond.”

The FAA said it “will continue to meet our responsibility to hold airlines accountable, while standing ready to collaborate where appropriate so that Americans can confidently expect safe, reliable, and affordable service whenever they purchase an airline ticket.”

U.S. Transportation Secretary Pete Buttigieg, who met June 16 with airline CEOs on summer travel issues, told CNBC on Tuesday that “air traffic control staffing issues do not explain the majority of delays and cancellations we’ve been seeing.”

U.S. airlines have cut about 15% of planned summer flights, an airline trade group said last month, while United has temporarily halted 12% of departures from its Newark hub alone because of congestion.

Over the four-day July Fourth holiday weekend, 8.8 million passengers were screened by the U.S. Transportation Security Agency (TSA) checkpoints, topping 2020 and 2021 but around 12% lower than 2019 levels.

Roitman estimated “over 50% of our delay minutes and 75% of our cancels in the past four months were because of FAA traffic management initiatives.”

He said United performed better than major rivals over the holiday weekend but added “we still have some work to do to meet standards of reliability and operational performance.”

Last month, an airline industry trade group said the FAA must ensure adequate air traffic control staffing to avoid further summer travel disruptions, saying a key Florida center had been “understaffed for 27 of the last 30 days, which is crippling to the entire east coast traffic flows.”

(Reporting by David Shepardson; Editing by Himani Sarkar and David Gregorio)

---