Smoke that filled the business class cabin of a Swiss International Airlines plane and forced an emergency landing was caused by a damaged headphone case, the airline said. After landing, technicians found a headphone charging case had slipped between two seats, where it had become damaged. While most airlines forbid power banks from being stowed in the hold, they allow them to be brought on as carry-on luggage. Swiss, however, banned their use in the cabin at the start of the year, although passengers can bring them with their hand luggage. Citing Bangor airport spokesperson Aimee Thibodeau, the Daily Express reported that the incident led to the temporary closure of one of the runways.