• The flight attendants' union said resuming alcoholic sales is "unsafe and irresponsible."
• Southwest suspended alcohol sales in March 2020.
• The airline extended the suspension last spring because of a surge in unruly travelers.

Southwest Airlines will resume alcohol sales on most of its flights this month after nearly two years, a pause it extended last spring because of a surge in disruptive passengers.

The move further heightened tension between the airline and its 16,000-member flight attendants' union, which called the resumption of alcohol sales "unsafe and irresponsible."

The Dallas-based airline originally paused alcohol and other services in March 2020 at the start of the pandemic. Last week, the airline's COO said the carrier would likely bring alcohol sales back late in the first quarter or early in the second quarter.

Starting Feb. 16, Southwest will sell alcohol, including beer, wine, rum, tequila and vodka on flights at least 176 miles long. It is also said it will also add tonic water, apple juice, Coke Zero, Dr. Pepper, hot tea and hot cocoa to current lineup of non-alcoholic beverages.

All U.S. airlines slashed onboard service during the pandemic and food and other beverage services are starting to make a comeback.

American Airlines and Alaska Airlines scaled back some recent service expansions under pressure from flight attendants unions, which argued it would increase the amount of time passengers would not be wearing face masks, which are federally mandated on board, though they can be lowered when drinking or eating. The mask mandate is in effect through at least March 18.

Southwest is facing similar pressure from its flight attendants' union, TWU Local 556.

"We have adamantly and unequivocally informed management that resuming sales of alcohol while the mask mandate is in place has the great potential to increase customer non-compliance and misconduct issues," said Lyn Montgomery, president of Southwest flight attendants' union.

Southwest declined to comment on the union's statement.

Southwest and American Airlines last May said they would hold off on plans bringing back alcohol, in American's case to domestic and short-haul international coach, because of disruptive passenger behavior that in some cases included physical assault against crew members.

"Customers have expressed a desire for more beverage options, so we're delighted to restore additional on-board offerings as a part of the Southwest Hospitality that our Customers know and love," Tony Roach, Southwest's vice president of customer experience and customer relations said in a statement.