Incident Description
Ozark Flight 709, a DC-9 aircraft registered as N923L, was operating under radar control of Kansas City Air Route Traffic Control Center (ZKC) and had been cleared to cruise at Flight Level 270 (FL270). While proceeding east-southeast near the boundary of the ZKC area, the DC-9 converged with a flight of three F-4 fighters designated Zorro 11.
The F-4s had been cleared by Indianapolis Air Route Traffic Control Center (ZID) to proceed westbound at FL260 to rendezvous with a KC-135 tanker, call sign Shake 81, for aerial refueling on route AR110W. The beginning of AR110W was within the ZID area, and the route continued westbound into the ZKC area. The tanker was orbiting under the control of ZKC and had been cleared to maintain a block altitude of FL260 to FL290.
Sequence of Events
ZID cleared the F-4s to contact the tanker frequency without handing them off to ZKC and without obtaining approval from either ZKC or the tanker. After establishing radio contact, the tanker crew incorrectly cleared the three F-4s to climb to FL270. When the ZKC controller realized that the F-4s and the DC-9 were converging, he instructed the DC-9 crew to immediately turn left. The DC-9 crew saw the F-4s and took evasive action.
Coordination Issues
ZID had not properly coordinated the F-4s' position with ZKC or the tanker. None of the pilots (for the DC-9, F-4s, or tanker) were informed of conflicting traffic. The lack of coordination between the two air traffic control centers and the incorrect clearance by the tanker crew led to the aircraft converging at the same altitude.