Most airlines aren't serving booze during the pandemic. Passengers are (illegally) bringing their own.

Airline passengers have long tucked those miniature bottles of booze into their carry-on bags or filled a to-go cup with cocktails so they don't ring up an in-flight bar tab, federal regulations against it be damned.

The practice has spiked during the pandemic, but for a different reason: most airlines aren't serving alcoholic beverages in the name of limiting contact between flight attendants and passengers.

And at least one airline is fed up.

Southwest Airlines, responding to an increase in reports from flight attendants about passengers consuming their own alcoholic beverages on the plane, is permanently adding a new line to its in-flight safety announcements, according to a memo sent to flight attendants Thursday by Kari Kriesel, Southwest's manager of inflight safety, standards and regulatory compliance.

The gist: you can't BYOB. Well, you can bring it, but you can't drink it on the plane.

After passengers are reminded about no smoking, using electronic cigarettes or tampering with the smoke detector in the lavatory, flight attendants will announce: "It is also prohibited to consume alcohol that you've brought.''

Kriesel's memo attributed the increase in passengers bringing their own alcoholic drinks on board to the lack of in-flight drink sales and availability of alcohol in airports during the pandemic. Southwest is only serving passengers a cup of water and a package of snack mix.

She said most airlines are "noticing the same challenges.''

American Airlines has seen an increase in incidents, too, spokesman Ross Feinstein said.

Southwest seemed to give most passengers the benefit of the doubt, suggesting they might not be aware of the policy rather than flaunting it.

"While there is information on Southwest.com and announcements are made in the gate area, some customers may not know about this regulation that prohibits them from consuming their own alcohol,'' Kriesel said in the memo.

What happens to passengers caught with their own drinks? Southwest told its flight attendants to "use their hospitality'' to explain the policy and ask the passenger to discard the beverage.

"Refrain from confiscating sealed containers, and allow customers to stow those for the remainder of the flight,'' the memo said.

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