"This is your pilot speaking - you are free to change your shorts."

British Airways Plc is investigating an incident in which an emergency alarm was sounded in the cabin of a Boeing Co. 747 warning passengers that the jumbo jet was about to make an emergency landing on water.

The button that played the message on the flight from London to Hong Kong on Aug. 24 can be activated in a number of ways, but isn’t accessible to pilots in the cockpit, British Airways spokesman Richard Goodfellow said today in an e-mail.

“Our cabin crew immediately made an announcement following the message advising customers that it was played in error and that the flight would continue as normal,” he said.

London-based British Airways is looking into exactly what happened and apologizes to passengers for causing “undue distress,” he said.