(NewsNation Now) — After getting billions in COVID-19 relief funds, the airlines are still struggling to keep pilots, flight attendants and other staff, which is affecting holiday travel plans across the country. What happened to the money?

The CEOs of the four largest airlines, American, United, Southwest and Delta tell Congress that while the Payroll Support Program was a success, the buyouts and other measures they were forced to resort to during the early months of the pandemic are having a ripple effect and affecting their ability now to staff up for the holiday travel season.

The executives say that the $54 billion in CARES Act funding they received at the onset of the pandemic saved nearly 400,000 jobs.

However, the airlines are still having trouble hiring back enough personnel to operate at full bore now that travel bans are lifting and America and the world are traveling again. United alone has grounded at least 100 planes because there just aren’t enough personnel to fly them.

Current employees are reluctant to pick up extra shifts, in part due to the risks of COVID-19 and the dramatic rise in air rage incidents, which the executives blame largely on airport alcohol serving procedures leading to a greater incidence of passengers boarding planes intoxicated.

The execs also raised concerns about the rollout of 5G technology by Verizon and AT&T that they say could affect altimeters and other vital airliner control systems. United Airlines CEO Scott Kirby claims that up to 4 percent of flights could be canceled, delayed or diverted. The wireless industry said those claims are false, and that the airline industry is relying on “discredited information.”

To close with some news that people not in control of major airlines or cellphone companies can use: The busiest upcoming travel day is expected to be Dec. 23, no doubt to clear the skies for a certain fat man in a sleigh the next evening.