They were taking photos and striking poses – on a wing of a Boeing 777 aircraft in Buenos Aires, Argentina.
Now, at least two crew members of Swiss International Air Lines have landed themselves in trouble and are under investigation, according to media reports.
In a viral video that began circulating earlier in August, a female flight attendant is seen dancing and posing for a photo on the wing.
A man, who is reportedly a senior cabin chief, later joins the flight attendant and starts striking bodybuilding poses.
The flight attendant then leaves the aircraft by an overwing emergency exit.
In the video, two ground crew members can also be seen posing in front of the aircraft engine, as another ground crew member takes photos of them.
The video appears to have been taken at an airport terminal.
The incident took place just before the flight departed on Aug 16, said American news outlet Insider.
No passengers were on the plane when the crew embarked on their stunt, said the news report.
A representative for the airline strongly criticised the cabin crew’s antics and said that their behaviour would not be tolerated.
“What looks like fun in the video is actually life-threatening,” said Swiss International Air Lines spokesman Michael Pelzer in a statement to Insider.
“The wings of a Boeing 777 are at a height of about 5m. Moreover, after landing, even in high temperatures, the wings may be covered with ice. A fall from that height onto the hard surface can be devastating.”
The airline has been in contact with the flight attendants in question, said Mr Pelzer.
He also said that the airline crew should set foot on a plane’s wing only in the event of a dire emergency, such as evacuations, reported the New York Post.
Mr Martin Knuchel, the airline’s vice-president and head of cabin crew, criticised the behaviour of the crew.