The incidents come amid heightened fears of terrorism after the deadly attacks in Paris on Friday, which killed 129 people.
A passenger on the flight from Los Angeles, Keith Rosso, told NBC News that about two hours into the flight, as they were having a meal in business class, flight attendants hurriedly grabbed plates and announced the plane was making an emergency landing.
Buses were waiting when the plane arrived in Salt Lake City, and passengers were taken to another location, to be interviewed, Rosso said.
Air France Flight 55 from Washington Dulles had 234 people aboard, and Flight 65 from Los Angeles had 473 aboard, Paumier said. Flight 55 was a Boeing 777 and Flight 65 was an Airbus 380.
Todd Palmer, special agent for the FBI Salt Lake City field office, said Tuesday night that "law enforcement personnel have conducted intensive security checks ... and have not located any evidence which would lend credibility to the threats."
The Royal Canadian Mounted Police said it was using police dogs trained to detect explosives to sweep the plane that landed at Halifax as a precaution.
Earlier Tuesday, there was a security scare aboard a London-to-Boston British Airways flight after a woman allegedly tried to open the plane’s emergency exit door mid-flight, officials said.
Massachusetts State Police said in a statement Tuesday that the passenger “was intoxicated” and there was no link to terrorism.
Russian officials confirmed Tuesday that a passenger jet that crashed in Egypt Oct. 31 was brought down by a bomb. The terror group ISIS has claimed responsibility for that crash, which killed all 224 people on board.
Becky Bratu is a staff writer at NBC News covering national, international and breaking news for NBCNews.com. She joined NBCNews full-time in November 2011, and previously worked within the company as a Web producer for "Nightly News with Brian Williams" and "Rock Center with Brian Williams." She began working at Rockefeller Center as an intern in June 2011.
Bratu previously worked for newspapers and television stations in Romania and Germany, and did a stint as a blogger and Web producer for a tech and social media start-up in Virginia.
She comes from Arad, Romania, and attended Columbia University in New York and Washington and Lee University in Virginia.
Jay Blackman is an NBC News producer covering such areas a transportation, space, medical and consumer issues.