Buy a ticket on a flight your favourite band will be on, take their photo, get off the plane and get a refund on the ticket. What could possibly go wrong?

Three fans came up with their cunning plan after they learned that pop band Wanna One was going to be on Seoul-bound Korean Air flight in Hong Kong on Saturday. They refused to sit down and instead took pictures of the 11-member band. 

Once they got their photo, the fans - in their 20s - insisting on getting off the flight and demanded a refund on their tickets.

The rest of the 360 passengers had to disembark and go through security screening again, delaying the flight by almost an hour, the company said in a statement.

Korean Air Lines Co Ltd was less than amused by the stunt and said on Tuesday it would raise penalties for cancellations.

"The fact is there were passengers who falsely checked in on the flight to see celebrities," a Korean Air official told Reuters.

The company said all passengers have to go through screening again if some passengers get off voluntarily.

The airline will charge an additional 200,000 won ($177) to passengers who cancel international flights from January 1.