Two planes were evacuated upon arrival at Seattle-Tacoma International Airport on Sunday due to what a spokesman called a "security concern."

Airport spokesman Perry Cooper says a JetBlue flight from Long Beach, California, and a regional SkyWest jet from Phoenix were the planes involved. The flights arrived late Sunday afternoon.

Cooper said that as a precaution, passengers were bused to their gates from the airport's third runway. He said the matter was under investigation and that he did not have further details.

Additionally, a Delta Air Lines spokesman says a flight from Los Angeles to Orlando was diverted to Dallas Sunday afternoon due to "a security concern."

Spokesman Morgan Durrant said passengers on Flight 1061 got off the Boeing 737-900 so authorities can search the aircraft. The airline plans to continue the flight when authorities determine it is safe to do so.

Laura Eimiller, a spokeswoman for the FBI in Los Angeles, said online threats targeted the JetBlue and Delta flights. She said there was no known threat to any aircraft that departed from the Los Angeles area and that as part of the investigation agents will determine whether the threats were related.

The flight disruptions come a day after bomb threats targeted two jets bound for Atlanta, prompting F-16 fighter jets to escort the planes. The threats posted on the social media network Twitter targeted Southwest Airlines Flight 2492, which arrived at Atlanta from Milwaukee; and Delta Air Lines Flight 1156, which arrived from Portland, Oregon.

It was unclear if any of threats were connected.