(REUTERS) - Airlines cancelled over 700 flights in the United States on Monday (June 27), as adverse weather and a shortage of staff hurt their ability to keep up with a surge in summer travel demand.

Total flight cancellations within, into, or out of the United States as of 1.07pm ET were 747, as per flight-tracking website Flightaware.com.

Nearly 860 flights were cancelled on Sunday.

Delta Air Lines had over 200 cancellations, Republic Airways and United Airlines had 196 and 122 flight cancellations, respectively, while American Airlines cancelled 62 flights as of Monday afternoon.

American Airlines said the cancellations were largely due to weather and air traffic control initiatives designed to regulate traffic. Delta, United and Republic did not respond to Reuters requests for comment.

In Europe, recent airport snarls have been blamed on a shortage of employees, as many workers, who were laid off during the pandemic, desert airport work for flexible working practices and other occupations.

Even the US regulator Federal Aviation Administration (FAA) faces staff shortages.

The FAA last week granted United approval to temporarily cut Newark flights after the Chicago-based carrier petitioned for a waiver, citing airport construction and air traffic control staffing.

Airlines for America, a trade group, said on Friday the FAA must ensure adequate air traffic control staffing to avoid further summer travel disruptions.

Shares of Delta, United and American Airlines were down 2% to 3% in afternoon trade.