Apparently a passenger onboard was exhibiting "suspicious behavior" -- although I'm sure there's more to the story since the plane was diverted to Maine, so it was quite a ways into the flight. http://www.boston.com/metrodesk/201...urity-issue/EG4PgBqjKAanGv1qPGkEbJ/story.html
Some more details from CNN say the passenger in question is a woman and that she handed the FA a note that said she had a "surgically implanted device", which obviously got the ball rolling. She's supposedly a French citizen from Cameroon traveling to the US for 10 days without any checked luggage. As always, the news wanna be first rather than accurate, so chances are the real story will take some time to come out.
Will all flights to/from South Korea be cancelled now? http://www.economist.com/blogs/graphicdetail/2012/04/daily-chart-13