# 2006 O'Hare International Airport runway incursion

On July 23, 2006, a United Airlines Boeing 737 operating as Flight 1015 nearly collided with an Atlas Air Boeing 747 operating as Flight 6972. UAL1015, bound for Denver International Airport, was carrying 120 passengers and 7 crew members whereas GTI6972, originating from Frankfurt Airport, Germany, was carrying 4 crew members only. The near miss occurred at the intersection of Runways 27L and 14R at O'Hare International Airport.

## Aircraft

The first aircraft involved in the near miss was a 19-year-old Boeing 737-322 with serial number 23947 and was registered as N315UA. It was manufactured by Boeing Commercial Airplanes in 1987 and was powered by two CFM International CFM56 engines.$^{:1}$
The second aircraft involved was a 4-year-old Boeing 747-47UF with serial number 32840 and was registered as N418MC. It was manufactured by Boeing Commercial Airplanes in 2002 and was powered by four General Electric CF6-80 engines.$^{:2}$

## Incident

O'Hare International Airport was ranked as the sixth busiest airport globally. Due to this, the control tower was usually split into two or more positions to relieve stress and congestion. However, on the day of the incident, the North Local Control Tower (NLC) was closed. Therefore, the South Local Control Tower (SLC) was bearing all the responsibilities on their backs, including aircraft landing on Runway 14R and departing from Runway 27L. As a result, two additional controllers were required to assist the SLC.
The weather conditions were extremely favorable that day, with excellent visibility. At exactly 21:57:28 Central Time Zone, the flight crew of Atlas Air Flight 6972 established initial contact with the SLC tower to request permission to land on Runway 14R. The SLC clears the flight to land and advises them of another traffic departing on the same runway: United Airlines Flight 938. Around 22 seconds later, the SLC clears UAL938 for departure. At 21:57:20 CST, as UAL1015 is holding short on Runway 27L, the SLC instructs UAL1015 to line up and wait at the runway. Finally, at 22:00:22 CST, the crew of UAL1015 was cleared for takeoff on Runway 27L. Atlas Air Flight 6972 touches down at around the same time on Runway 14R. Everything runs smoothly for UAL1015 until the airframe reaches 110 knots. The pilots of UAL1015 noticed that the Boeing 747 was approaching the Runway 27L-14R intersection. They decided that they weren't going to abort the takeoff and soon, it became clear that they'll have to rotate above him. Ten knots prior to the Vr speed, the aircraft lifted off and overflew GTI6972 with only 35 feet to spare. Flight 6972 was completely on Runway 27L when the Boeing 737 was lifting off.$^{:3–4}$

## Analysis

According to the analysis, before United Airlines Flight 1015 was given permission for takeoff, the air traffic controller was facing a ton of distractions. When UAL1015 asked permission for takeoff, the SLC glanced out the window to Runway 14R and didn't spot an aircraft. Then he was verifying the distance of United Airlines Flight 938, the aircraft which departed Runway 14R, to ensure adequate wake turbulence separation. All of this was done in about 3–4 seconds.$^{:3–4}$

## Aftermath

After the investigation, the National Transportation Safety Board (NTSB) concluded that the South Local Control Tower's (SLC) failure to monitor Atlas Air Flight 6972 and United Airlines Flight 1015 caused a loss of separation between the two aircraft.$^{:12}$