Everyone knows that famous flight scene in Bridemaids where Kristen Wiig's character has a few too many shandies.
It's easily done when you're cramped in a small space for many hours, with limited options to keep you entertained.
An anonymous American Airlines flight attendant has revealed how cabin crew keep in-flight boozing under control.
"When you think about it, being on board an aircraft is really one of the only situations in which it's vaguely socially acceptable to day-drink by yourself," she told MailOnline Travel.
"The majority of passengers who drink will have two. One when service commences and another one with a meal. Then there are always the ones who can knock back four. It's easy to overdo it."
She said they use a "traffic light system" to monitor passengers. If you're "green", they'll keep serving you, if you're "yellow" they'll slow you down.
When you're "red" - glassy-eyed, unsteady and slurring - they'll stop giving you grog.
"It's a red flag if someone is getting up to use the lavatory more often than normal," she said.
"Or when they start pulling seemingly sly tricks.
"People often think they can sneak in extra drinks by requesting them from a different flight attendant each time. Actually, you're just drawing more attention to yourself."
However, telling someone to stop can get awkward.
"It's embarrassing for all involved," she admitted.
"I quite often just pretend I haven't noticed the passenger who's waving me down for another drink until they give up. That or I just 'forget' their order."