ATLANTA -- U.S. officials scrambled two F-16 fighter jets to shadow a pair of commercial airliners after bomb threats were made Friday against the flights on the social network Twitter.

The planes landed safely and law enforcement officials found no bombs aboard after they arrived safely at Atlanta's main airport, said airport spokesman Reese McCranie.

The threats targeted Southwest Airlines Flight 2492, which arrived from Milwaukee, and Delta Air Lines Flight 1156, from Portland, Oregon.

The passengers were taken off the aircraft, and police bomb and dog teams examined both planes, authorities said.

The threats were posted on the social media network Twitter, said Preston Schlachter, a spokesman for the North American Aerospace Defence Command. After being alerted, military officials sent two F-16 fighter jets from a base in South Carolina to escort the commercial aircraft to Atlanta.

Upon landing, the Southwest Airlines flight taxied to a remote area where the passengers and the aircraft were rescreened, company officials said in a statement.

"Our top priority is the safety of our customers and employees," Southwest officials said. "We cannot comment on the nature of the security situation."