A United Airlines flight from Chicago to Germany was forced to make an emergency landing in Toronto when the captain spilled his coffee on the instrument panel, causing the radio to shutdown and an automated hijacking alert to go out.  From the Transport Canada report:

United Airlines said flight UAL940, a Boeing 777-200 with 241 passengers, was flying east over Kingston at about 9 p.m. ET Monday when the pilots started having problems navigating and using the plane’s communications equipment. The plane began sending out alerts that it had been hijacked and had lost communication. The pilots tried to return to Chicago but made an emergency landing at Pearson International Airport instead.

I’m not a pilot myself but I have had my share of drink spills while operating a vehicle and they are never good.  Given that in this case several hundred lives were at stake I’d say it’s worth laying down the cash for a spill proof mug.

Via  The Province