The FAA is investigating whether garbled transmissions and too-similar flight numbers may have led to a close call at Chicago’s Midway Airport.
Just before 7:40 (8:40 p.m. ET) Tuesday evening, a Southwest Airlines flight bound for Tulsa was cleared for takeoff on Runway 31-Center. As that plane began its roll, the FAA says controllers noticed that a Delta flight, departing Chicago for Atlanta, had begun rolling on Runway 4-Right without clearance. Both aircrafts were heading for the same intersection.
"The controller alerted the Delta crew to stop immediately,” the FAA said in a statement. "The Southwest crew chose to stop as well. Each aircraft halted more than 2,000 feet from the runway intersection."
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Tower tapes available from LiveAtc.net suggested nothing was amiss as the Southwest flight was given its takeoff clearance. But because of garble on the frequency, the air traffic controller handling the flight repeated his instruction.
"Did you call Southwest 3828?" he says. "Verify no delay, left at two-five-zero. Three one center, clear for takeoff."
Shortly after that, the frightening moment when the controller saw two planes heading for the same intersection.
"Stop, stop, stop!" he is heard shouting on the control tower frequency. And shortly afterward, when both planes had halted their takeoff rolls, the Southwest captain inquires about who broke the rules.
"Were we the ones cleared for takeoff?" he asks.
"Yes sir you were," the controller responds. "You were the ones who were doing what you were supposed to be doing."
The Southwest pilot asks, "That Delta took our…Delta was rolling also?"
"Yep, he took your call sign," the controller says. "Somebody kept stepping on you. I couldn't figure out who it was. That’s why I reiterated that it was you that I was clearing for takeoff."
Earlier, as both aircraft were departing the gate, a ground controller warned both to be aware of their similar flight numbers.
"Delta 1328, be advised similar call sign on frequency is Southwest 3828," she advises. Then moments later, she tells the Southwest captain, "Be advised similar call sign on frequency, is Delta 1328."
Both captains acknowledged the warning.
In a statement, Delta Airlines said it was cooperating fully with the FAA’s investigation. Southwest emphasized in their own statement that safety is the airline’s number one priority, as they lauded the controller’s professionalism.
"After being cleared for takeoff at MDW on the evening of Tuesday, June 16, the pilots of Southwest flight 3828 followed FAA Air Traffic Control instructions and safely aborted takeoff," the statement said. "Then the pilots proceeded to taxi off of the runway to complete required checklist items, and returned to the terminal to complete other necessary reports and tasks related to the event."
Both flights eventually continued on to their destinations without incident.