One day after pilots at Delta Air Lines authorized a potential strike, United Airlines pilots rejected a tentative contract agreement, setting the stage for possible work stoppages as the busy holiday travel season approaches.

Delta pilots voted Monday for a strike if necessary in order to secure a new contract with the nation's second-largest carrier. Negotiations to update pay and benefits between Delta pilots and the carrier, last settled in 2016, resumed in January following a two-year suspension due to the Covid-19 pandemic.

“Today, Delta’s nearly 15,000 pilots sent a clear message to management that we are willing to go the distance to secure a contract that reflects the value we bring to Delta Air Lines as frontline leaders and long-term stakeholders,” said Capt. Jason Ambrosi, chair of the Delta Master Executive Council, in a statement.

“Delta has rebounded from the pandemic and is poised to be stronger than ever, posting record revenues for the third quarter. Meanwhile, our negotiations have dragged on for too long."

In a follow-up interview, Evan Baach, a Delta pilot and Air Line Pilots Association (ALPA) union spokesperson, told NBC News the pilots want a contract, not a strike. He said the two sides remain at an impasse on issues like compensation.

In a statement, Delta said Monday's strike authorization vote would not affect customers and that under federal labor law, a strike cannot occur until certain conditions are met.

Airlines prepare for holiday travel chaos

Oct. 27, 202201:32

"Delta and ALPA have made significant progress in our negotiations and have only a few contract sections left to resolve," Delta said. "We are confident that the parties will reach an agreement that is fair and equitable, as we always have in past negotiations.”

On Tuesday, United Airlines pilots voted to reject a new agreement with the Chicago-based carrier, the nation's fourth largest. According to a statement, pilots will immediately begin a series of informational picketing events as they work to rally support.

"By the Company’s own admission, this agreement missed the mark," said United Master Executive Council chair Capt. Mike Hamilton in a statement. "That’s why both parties agreed to reengage at the bargaining table for a new, improved agreement."

A spokesperson for ALPA declined to comment further on the United negotiations. United declined to comment.

Meanwhile, American Airlines pilots, represented by the Allied Pilots Association, remain in their own negotiations with the nation's largest carrier.

Allied spokesperson Dennis Tajer told NBC News that union leadership is now weighing a possible tentative agreement. He said pilots across the industry are looking for greater schedule flexibility that can help meet the unprecedented demand that air travel carriers have experienced as the Covid-19 pandemic appears to wane. Pilot scheduling issues are one of the reasons air travel in 2022 has been beset by delays and cancellations, he said.