As water gushed into the New York City subway system during the flash floods that occurred during torrential rains this week, videos on social media showed dramatic scenes of water pouring across subway floors and passengers standing on the orange seats.

One lighthearted video captured water bubbling up outside the train’s windows as a woman rested her bare feet in the floodwater. The video was set to an unexpectedly upbeat song, “Hold My Hand,” by Jess Glynne, while a British woman enthusiastically announced, “Nothing beats a Jet2 holiday.”

What?

The popular TikTok “sound” has gone viral in recent weeks, with users adding the music and narration from a January 2024 airline ad campaign to videos, including dicey vacation moments.

The original campaign for Jet2holidays, Britain’s largest tour operator, showcased a deal offering 50 pounds (about $67) off holiday packages that included up to 22 kilograms (or 48.5 pounds) of luggage. The 30-second ad has been viewed more than two million times on YouTube.

So how did the tagline from a random ad from over a year ago become this summer’s ubiquitous travel meme?

The TikTok “for you” page prioritizes content that is doing well, regardless of the time it was first uploaded, allowing users to rediscover older material and create new content incorporating it, leading to a potential snowball effect.

Part of the appeal of the trend, said Jenna Jacobson, an assistant professor at Toronto Metropolitan University who specializes in social media, is its paradoxical nature — pairing a fun, lively audio with chaotic events.

“You don’t need to learn a fancy dance or anything that’s complicated. You can put it with a really boring video that everyone’s experiencing,” she said. “And it builds into this remix culture.”

And much like the unofficial, crowdsourced competition for “song of the summer,” awarded to whatever catchy pop song becomes the most inescapable, a social media trend like the Jet2holidays ad remixes can spread quickly at a time when many people are sharing videos of summer escapades.

Jet2holidays is not the only beneficiary of the ad’s sudden virality. Zoë Lister, the actress who narrated it, recently created a TikTok video introducing herself as the voice of summer fun, and saying that she has received messages from people in Brazil, Canada, Algeria and the Philippines, to name a few.

She even joked that she could not believe people in the United States were interested in the trend seeing as “they don’t even have holidays, they have vacations.”

Follow New York Times Travel on Instagram and sign up for our Travel Dispatch newsletter to get expert tips on traveling smarter and inspiration for your next vacation. Dreaming up a future getaway or just armchair traveling? Check out our 52 Places to Go in 2025.