(NEW YORK) — As U.S. air carriers see record pandemic-era travel, customers are taking to social media to vent their frustration over two-, three- and four-hour wait times to reach a reservation agent at the nation’s largest airlines.

When air travel came to a halt in March 2020, thousands of employees were offered early retirements and buyouts, but now the airlines are desperate to again fill these positions — especially for reservation agents — but it’s proving difficult.

On Tuesday morning, a customer could expect a call back from Delta Air Lines after three hours of waiting. Over Memorial Day weekend, Delta’s automated service told customers the wait time was more than 21 hours.

In a statement to ABC News, Delta acknowledged its challenges.

“We apologize to our customers for the inconvenience as our wait times are not currently where we’d like to them to be,” an airline spokesperson said. “We are seeing a higher call volume as more customers are beginning to travel, so we’re adding staffing through more scheduled hours and overtime for our specialists, hiring temporary summer contract workers and fast-tracking technology upgrades to reinforce existing self-service options to assist with travel needs.”

American and United customers are also seeing extended wait times. American said its reservation lines are now receiving more volume than they did in 2019.

American Airlines told ABC News it’s taking the unprecedented step of temporarily bringing back up to 200 of its reservation agents who had accepted early retirements/buy-outs last year. The airline plans to keep the agents working through the busy summer months while it hires and trains hundreds of new agents. Twenty-five percent of American’s reservations agents took buy-outs last year, according to the airline.

United Airlines said it’s also increasing its staffing and adding new technology to cut down on wait times.

However, hiring airline reservations agents can take months. And after the initial interview process, applicants must pass drug and background checks. American then said it takes four weeks of classroom training before an agent can take calls.

Airlines said customers calling in for COVID-19 travel information, questions about international travel restrictions and when routes will open are adding to the wait times.

Airlines recommend finding that information online, adding that any customer trying to change, book and search for flights should first try using their apps. The major carriers also offer a call-back option with an approximate wait time. American will allow you to schedule a time within seven days for a call back.

If your flight is departing with 24 hours and you need immediate assistance, reach out to your airline on social media for near-immediate assistance.

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