US airline flights land in Atlanta after bomb threats

Bomb threats against two US airline flights on Saturday prompted North American air defense fighter planes to scramble to accompany them to their destination in Atlanta, an airport spokesman said.
The planes landed safely at Hartsfield-Jackson International Airport, no bombs were found aboard either and the Atlanta airport has returned to normal operations, said airport spokesman Reese McCranie.
Threats against Delta Air Lines flight 1156 had been deemed credible, McCranie said.
Several media outlets reported that a Twitter user going by the name Zortic wrote of planting bombs on the two planes, stating in a message to a Delta Twitter account, "I have a bomb on one of your planes, but I forgot which one when I left the airport. Can you help me find it?"
Those tweets have since been deleted.
Neither the Federal Bureau of Investigation, which is leading the investigation, nor the airport confirmed the source of the threats.