Two passengers were arrested after making threatening remarks to flight attendants on separate flights in America and Argentina.
Japanese tourist Yasuaki Ichimura was removed from an American Airlines flight from Miami to Seattle before takeoff.
He reportedly made derogatory remarks and told a flight attendant, "If I was a terrorist, I would blow up this airplane."
This followed a confrontation Mr Ichimura had with flight attendants about a carryon luggage that exceeded airline regulations.
Police notified the Japanese Embassy and sent him to a Miami-Dade County jail, where he was held on charges of making a false report.
Airline spokeswoman Minnette Velez said American Airlines refunded his ticket.
In another incident, a nonstop New York-Buenos Aires flight was diverted to Miami after a man who said he lost two friends in the World Trade Center attacks said the flight would end in a "fireball," an FBI agent said.
Rodrigo Deambrosio Zas allegedly told a flight attendant, "You don't know what I put on this plane. And if you stay on this plane to Buenos Aires, you'll find out."
The pilot diverted the flight after warning Mr Deambrosio that he would stop in Miami and get him off the plane. The co-pilot and flight attendants also talked to Mr Deambrosio.
In attempts to control Deambrosio's outbursts, one attendant sat with him and another sat behind them with a pair of handcuffs from the cockpit. He told a flight attendant that he had taken cocaine and two sleeping pills and had been drinking before and during the flight.