Few prospects are more terrible to a traveler than being separated from their luggage — except maybe being on an aircraft with luggage separated from its owner.

About one hour into a Norwegian Air flight from London to Boston earlier this month, crew discovered that they were transporting a piece of luggage without its owner.

When the airline discovered that the passenger was not on board, pilots performed an emergency diversion to Ireland. However, the Dublin detour was not meant to reunite the passenger with their lost piece of luggage. It was performed as a security measure.

Man looking at airplane take-off
Credit: Corbis/VCG/Getty Images

“The passenger whom the luggage belonged to was not on board the aircraft, which is why this security measure was taken,” the airline said in a statement, according to The Telegraph. “We’re sorry about the inconvenience caused to the passengers.”

Regulations prohibit an airline from knowingly transporting luggage without a passenger across international borders. Standard operating procedure is to match luggage with passengers during the boarding and loading processes. If a passenger is not on the plane, grounds crew will “offload” their luggage.

But since the flight to Boston had already taken off, they had to divert.

There were 344 people onboard the plane when it diverted. The aircraft was on the ground at Dublin Airport for nearly two hours. It arrived in Boston about three hours late.