Air travelers have faced an unusually high number of disruptions this summer because of widespread labor shortages, bad weather, and technical problems. Nearly a quarter of U.S. passenger planes between June and mid-August were delayed, while almost 4 percent of flights were canceled in the first half of August, according to data from Flight Aware, a flight tracking service. Spirit alone canceled nearly 2,500 flights between Aug. 1 and 15. Flight attendants across the country say they are struggling to cope, facing not only these prolonged operational issues, but also an increase in aggressive passenger behavior. Nearly 4,000 unruly passenger incidents have been reported to the Federal Aviation Administration in 2021, a figure described by the agency as “a rapid and significant increase.”