By David Shepardson WASHINGTON (Reuters) – Two U.S. senators on Thursday urged airlines and regulators to take steps to reduce flight cancellations and delays after more than 2,700 Memorial Day weekend flights were cancelled. Travelers are bracing for a difficult summer as airlines expect record demand and are still rebuilding staff after thousands of workers left the industry during the COVID-19 pandemic. Democratic Senators Richard Blumenthal and Edward Markey asked Transportation Secretary Pete Buttigieg in a letter https://www.blumenthal.senate.gov/imo/media/doc/0602.22dotflightdelaysandca…