WASHINGTON, Nov 30 (Reuters) - The chair of the U.S. Senate Commerce Committee, concerned about worker shortages at airlines that received billions of dollars in government assistance, has invited CEOs of seven major U.S. carriers to testify at a Dec. 8 hearing, airlines and a committee official told Reuters. Senator Maria Cantwell, a Democrat who chairs the panel, is inviting the chief executives of American Airlines (AAL.O), Delta Air Lines (DAL.N), Southwest Airlines (LUV.N), United Airlines , JetBlue Airways (JBLU.O), Alaska Airlines (ALK.N) and Spirit Airlines (SAVE.N) to testify, the official added. The airlines declined to comment or did not immediately respond to requests for comment. Reuters first reported plans for the hearing on Nov. 3 but it was not clear at the time if Cantwell would ask the CEOs to appear. Starting in March 2020, Congress approved three separate rounds of taxpayer bailouts totaling $54 billion to cover much of U.S. airlines" payroll costs through Sept. 30 as a result of COVID-19.The heavy U.S. Thanksgiving travel week would not have been possible without the government payroll assistance program and union-negotiated incentives, Sara Nelson, president of the Association of Flight Attendants-CWA, representing workers at 17 airlines, said Tuesday in a statement. "We made sure aviation workers were in place to meet the return demand for air travel after access to vaccination," Nelson added. Last month, Nelsonnoted that the airline industry "created a COVID-19 relief plan that no other industry got." Airlines that received government assistance were not allowed to issue involuntary layoffs or cut worker pay. They also had to limit executive compensation and halt share buybacks and dividend payments. Staffing shortages in recent months have prompted some airlines to cancel hundreds of flights at times even as they worked to boost staffing. In July, Cantwell asked several airlines detailed questions about "workforce shortages, flight cancellations, and delays, creating havoc and frustrating consumers as more Americans resume travel." That letter said each airline "poorly managed its marketing of flights and workforce as more people are traveling, and, at worst, it failed to meet the intent of tax payer funding and prepare for the surge in travel." This month, Federal Aviation Administration chief Steve Dickson said difficulties with some airline operations are "due more to changes in consumer behavior" like a jump in leisure travel. "They probably don"t have as much buffer in their schedule as they had previously," he added. A group of U.S. senators this month led by Democrat Richard Blumenthal reintroduced legislation to expand protections for air travelers aimed at ensuring "airlines provide passengers with fair compensation, refunds, and recourse in the event of airline-caused flight delays and cancellations."