LONDON, June 21 (Xinhua) -- National holidays and a season of post-pandemic "revenge travel" have heaped pressure on already-strained U.S. airlines, the Guardian newspaper has reported.

       According to an article published on Monday, 4,200 U.S. flights were delayed and 900 canceled on Father's Day (Sunday), bringing the total number of flights interrupted since Thursday to 19,000. Juneteenth, a federal holiday in the United States commemorating the emancipation of enslaved African Americans, and the holiday weekend also contributed to the disruptions.

       "The travel conditions have been blamed on pilot and staff shortages, packed planes, and the logistical effects of bad weather," said the report.

       Quoting the U.S. Travel Association, the report said about 85 percent of Americans plan to travel this summer, after postponing holiday plans for two years during the pandemic. However, travel costs are likely to increase due to high fuel prices, the Guardian said, meaning some people will not be able to afford holidays.