One woman clocked more than 25 million impressions on her clip of the pillow hack. Photo, Screengrab TikTok/nolimitua

A sneaky travel hack is making the rounds on social media, but not everyone is impressed by it.

The viral act shows passengers stuffing their empty pillow case with clothes and then showing themselves successfully making it onto the aircraft without being stopped by cabin crew.

One TikTok user said the cheeky act saved her €80 ($120) in baggage fees.

"We tried the airport pillow hack," she said as footage showed her walking through a terminal.

She managed to get an extra 6kg onto the flight by loading her square-shaped pillow case with extra clothes. Her clip has had more than 3.3 million views.

Another travel blogger showed how she also got away with the act by sharing a viral clip clutching onto a clothes-filled pillow case on the plane.

One passenger, who's clip has been viewed a whopping 25.1 million times, described it as the "best travel hack ever".

"Pillow flies for free," she added, as she stuffed the case with clothes.

The hack has prompted some to give it a go, saying it is "genius".

"We are travelling from Canada to Mexico and I want to try this especially because we are bringing the children," one person commented.

"OMG this is another level – got [to] try this one," another added, while a third wrote: "Smart move."

However, not everyone was impressed, with some describing it as "embarrassing".

"Nah I'd rather pay the extra weight and save myself the embarrassment if caught," one TikTok user wrote.

"I'll be so embarrassed if it's now me that they catch," another said.

Others branded the act as "risky".

"These pillow hacks will soon be seen by airlines and they will start checking them," one said, while another added: "If all passengers do the same thing I think the plane will be overloaded and risk your flight. Be safe mate."

An airport staffer jumped into the comments section and said: "You know we actually see that you have clothes inside it when you put it through scanning."

Weight drives how much fuel the plane needs for a flight – that's why you'll see extra cargo or passengers (or both) offloaded so the aircraft can carry sufficient fuel to take off successfully.

Weight allocation for planes is a carefully calibrated art. If you ever wondered why you were allocated 7kg of carry on luggage it has to do with standard weight calculations.

Standard weight is the sum of passengers, crew and carry-on baggage and in Australia and New Zealand, the weight for carry-on baggage is set at 7kg per passenger.