Boeing 737-300 and Airbus Industrie 320-200 incident near Chicago, Illinois, March 23, 2006
On March 23, 2006 at about 3:07 pm local time, 2 aircraft, Boeing 737-300 (N309UA) and Airbus Industrie 320-200 (N493UA), were involved in the same incident near Chicago, Illinois. No one was hurt; 121 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The probable cause of this incident was the ORD tower local controller's failure to provide sufficient separation between two aircraft departing intersecting runways. Contributing to the incident was the ORD local monitor's failure to monitor the situating and advise the local controller of the developing situation.
The probable cause of this incident was the ORD tower local controller's failure to provide sufficient separation between two aircraft departing intersecting runways. Contributing to the incident was the ORD local monitor's failure to monitor the situating and advise the local controller of the developing situation.
Source: NTSB aviation accident database, copy made November 2, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- March 23, 2006 · about 3:07 pm local time · cases in 2006
- Place
- Chicago, Illinois · map
- Type
- Incident
- Injuries
- No one was hurt; 121 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft 1
- Boeing 737-300 · all 737-300s on the register
- Registration
- N309UA · registry record
- Damage
- Not recorded
- Flight
- Flight · scheduled airline rules (Part 121)
- Aircraft 2
- Airbus Industrie 320-200
- Registration
- N493UA · registry record
- Damage
- Not recorded
- Flight
- Flight · scheduled airline rules (Part 121)
The NTSB's narrative for the Boeing 737-300 final · quoted from the NTSB record
On March 23, 2006, at 0907 Central Standard Time, a runway incursion occurred between United Airlines (UAL) flight 604, a Boeing 737-300, and UAL1520, an A-320, at Chicago O'Hare International Airport (ORD) during daylight visual meteorological conditions. The north local controller cleared UAL604 for takeoff from runway 4L while UAL1520 was crossing the runway. The UAL604 co-pilot looked out the window and saw the A320 moving at a fast rate toward the runway, aborted the takeoff, and advised the controller that they were aborting their takeoff for the crossing traffic. The co-pilot stated that they did not get above taxi speed during their departure. Separation was lost with closest proximity of approximately 600 feet, the distance from approach end of runway 4L to taxiway H. AMASS did not activate.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The NTSB's narrative for the Airbus Industrie 320-200 final · quoted from the NTSB record
On March 23, 2006, at 0907 Central Standard Time, a runway incursion occurred between United Airlines (UAL) flight 604, a Boeing 737-300, and UAL1520, an A-320, at Chicago O'Hare International Airport (ORD) during daylight visual meteorological conditions. The north local controller cleared UAL604 for takeoff from runway 4L while UAL1520 was crossing the runway. The UAL604 co-pilot looked out the window and saw the A320 moving at a fast rate toward the runway, aborted the takeoff, and advised the controller that they were aborting their takeoff for the crossing traffic. The co-pilot stated that they did not get above taxi speed during their departure. Separation was lost with closest proximity of approximately 600 feet, the distance from approach end of runway 4L to taxiway H. AMASS did not activate.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record for the Boeing 737-300 from the NTSB's investigation tables, in plain English
Pilot
- Injury: no injuries
Co-pilot
- Injury: no injuries
The aircraft
- Landing gear: fixed
- Operator: United Air Lines INC
The flight
- Departed from: KORD Chicago IL
- Destination: KDCA Washington DC
- Flight plan: IFR
Weather at the time
- Wind: from 070° at 4 knots
- Visibility: 10 statute miles
- Sky: broken clouds at 2,600 ft
- Temperature: 39°F (4°C), dew point 27°F (-3°C)
- Altimeter: 30.25 inHg
- Observation at 8:56 am from KORD
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 5 | |||
| Passengers | 111 |
The factual record for the Airbus Industrie 320-200 from the NTSB's investigation tables, in plain English
Pilot
- Injury: no injuries
Co-pilot
- Injury: no injuries
The aircraft
- Landing gear: fixed
- Operator: United Air Lines INC
The flight
- Departed from: KORD Chicago IL
- Destination: KMCO Orlando FL
- Flight plan: IFR
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 2 | |||
| Passengers | 3 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Connections how this case links to the rest of the register
- N309UA on the register today · the tail number may have moved to another aircraft since
- Boeing 737 2,895 registered today · the model family and its accident history
- Boeing 6,677 aircraft on the register
- N493UA on the register today · the tail number may have moved to another aircraft since
- Airbus 1,507 aircraft on the register
- Chicago O'Hare International · departed from
- Ronald Reagan Washington Ntl Airport · bound for
- Orlando International · bound for
- Accidents and incidents in Illinois 2,118 since 1982 · 251 in the last ten years
- Illinois 8,061 aircraft registered
The whole map of how records connect · these connections as data: /graph/accident/OPS06IA007.json.
The bigger picture in Aviation Analytics: accidents over time since 1982, by model, by phase of flight and conditions, by place and on the map.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text does not name anyone involved, its policy at this time. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.