Spilt coffee in the cockpit of a United Airlines Boeing 777, and the inadvertent selection of the "hijack" transponder code, preceded diversion of the jet to Toronto.

Transport Canada says any investigation of the incident, which occurred on 3 January during a scheduled flight from Chicago to Frankfurt, rests with the Federal Aviation Administration and the airline.

According to a Transport Canada report, the crew advised that they were experiencing communication problems and, subsequently, navigation problems.

The crew then cycled through squawk code 7500, which signals a hijack, as well as 7600 for lost communication.

Transport Canada says supplemental information from the FAA revealed United had indicated that the captain "had inadvertently squawked a 7500 code after spilling coffee on the aircraft's radio equipment, which interfered with the communications equipment". But the crew subsequently confirmed the issue was navigational and communications related, and not a valid "7500" emergency. The crew then squawked the 7600 code and diverted to Toronto. Initially they attempted to return to Chicago.

Source: Flight International