WASHINGTON—U.S. lawmakers on Wednesday gave final approval to a new $14 billion payroll assistance package to U.S. airlines as part of a COVID-19 relief bill, the third round of government support to the struggling sector since March 2019. With the latest six-month extension that will keep thousands of workers on payrolls through Sept. 30, Congress has awarded U.S. airlines $54 billion for payroll costs since March 2020. U.S. air passenger travel fell by 60 percent in 2020 to the lowest level since 1984, down more than 550 million passengers. U.S. passenger airlines are still collectively burning about $150 million daily, and the cash bleed is expected to continue through most of this year as demand remains depressed. Airlines for America, an industry trade group, praised the latest extension, saying it “is vital to have our employees on the job and ready to assist as our nation prepares to move forward …