A stick of dynamite has been found in the luggage of an American college student flying from Argentina to the U.S. on Continental Airlines.
Authorities in Houston in the southwestern state of Texas found the explosive during a luggage search after bomb-sniffing dogs picked up the scent.
They say they student, who has been detained, claimed the material as a souvenir of his visit to a mine.
The incident was one of several security scares that forced the diversion, evacuation or delay of airline flights Friday:
An American Airlines plane, on a flight from Manchester, England, to Chicago was diverted to Bangor, Maine after authorities learned of an unspecified threat to the aircraft.
Earlier, Irish authorities evacuated an Aer Lingus plane at Shannon Airport following a bomb scare. An airport spokeswoman says the threat was called in to a police station in Dublin.
And a U.S. Airways flight had to be diverted to Oklahoma City after a passenger had a confrontation with a flight attendant.
Security has been increased at airports worldwide, following police raids in Britain earlier this month to break up what authorities said was a plan to bomb up to 10 U.S.-bound airliners over the Atlantic.
Some information for this report provided by AP and Reuters.