Investigation Summary
The accident was precipitated by a breakdown in communication between the O'Hare ground controller and the Delta crew. After landing on Runway 14L, Delta 954 reported being 'inside the bridge' and requested a holding area. The controller, missing the phrase 'inside the bridge,' assumed the aircraft was still north of the bridge near its landing runway and instructed them to hold in the 'thirty-two box.' In the controller's mind, this referred to the 32R run-up pad. However, the Delta crew interpreted this as the 32L run-up pad, which required them to taxi across Runway 27L. Crucially, the Delta crew had not been informed that Runway 27L was active for departures. As Delta 954 crossed the runway, North Central 575 was accelerating through 140 knots. The DC-9 captain spotted the Convair in the fog and attempted to rotate early to clear it, but the aircraft clipped the Convair's tail and wing. The DC-9 fell back to the runway, its landing gear collapsed, and it skidded into a grass area where it was destroyed by fire.
Final Conclusions
The NTSB determined the probable cause was the failure of the air traffic control system to ensure adequate aircraft separation during limited visibility. Contributing factors included the ground controller's use of non-standard and ambiguous terminology, the controller's failure to use available information (such as pilot reports and ground radar) to verify the aircraft's position, and the Delta crew's failure to request clarification of the ambiguous taxi instruction. The investigation also highlighted deficiencies in North Central's emergency evacuation training, as the DC-9 evacuation was slowed by a non-inflating slide and poor cabin visibility.
Video Analysis
Fateful Assumptions: The 1972 Chicago-O’Hare Runway Collision — A detailed analysis of the communication failures and procedural gaps that led to the collision of two airliners in dense fog at the world's busiest airport.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Delta Air Lines DL954 — Convair CV-880 · N8807E
North Central Airlines NC575 — McDonnell Douglas DC-9-31 · N954N
Crew Experience
Captain
Delta Flight 954
First Officer
Delta Flight 954
Captain
North Central Flight 575
First Officer
North Central Flight 575
Systems & Failure Modes
ASDE (Airport Surface Detection Equipment)
A ground radar system intended to help controllers track aircraft positions on the airfield; investigators found it was not properly utilized or required for controller qualification at the time.
Emergency Evacuation Slide
The DC-9's main entry door slide failed to inflate during the emergency evacuation, forcing the flight attendant to be pushed out and assist from the ground.
Interesting Facts
- 01Visibility at the time of the accident was approximately 1/4 mile due to dense fog.
- 02The ground controller assumed Delta 954 was at the 32R run-up pad, while the crew was actually taxiing toward the 32L pad.
- 03All 10 fatalities occurred on the North Central DC-9 due to fire and smoke inhalation during evacuation.
- 04The Delta Convair 880 was carrying 93 people; none were killed, though 10 were injured.
- 05Ground radar (ASDE) was available at O'Hare but was not being used effectively to monitor taxiing aircraft.
Safety Actions & Advisories
Standardization of Terminology
The NTSB recommended the elimination of non-standard colloquialisms and 'short-cut' phraseology in ATC communications.
Evacuation Training Improvements
The FAA required North Central Airlines to improve its training program to include simulated accident conditions and practical evacuation drills.
Ground Radar Procedures
Recommendations were made to standardize the use of ground radar (ASDE) and ensure controllers were qualified in its operation.