Authorities gave the all-clear on Wednesday after searching the two landed planes for threats, the FBI said in a statement.

The two Air France flights were both diverted safely around the same time on Tuesday night after receiving anonymous theats after take-off.

"As a precautionary measure and to conduct all necessary security checks, Air France...decided to request the landings of both aircraft," the company said in a statement.

US investigators found no explosives or other threats on board, however.

On Tuesday night, a Boeing 777 travelling from Washington, D.C. was diverted to Halifax, Canada, and around the same time an Airbus A-380 en route from Los Angeles to Paris was diverted to Salt Lake City, Utah.

All passengers disembarked safely upon landing and were taken to nearby terminals.

blc/msh (AFP, AP)