A routine arrival into Chicago took an unexpected turn on September 25th 2024, when an Envoy Air regional jet inadvertently touched down on the wrong parallel runway at O’Hare, an incident later attributed to cognitive bias in the cockpit and missed intervention from air traffic control.
The Envoy Air Embraer ERJ-170, registered N772MR, was operating flight AA-3936 on behalf of American Airlines from Norfolk, Virginia to O’Hare International Airport with 64 passengers and four crew members on board.
During descent, the crew was instructed to expect runway 10C and was subsequently cleared for the instrument landing system (ILS) approach to that runway. The clearance was acknowledged and correctly read back. The captain, serving as pilot monitoring, briefed the approach and programmed the flight management computer with the ILS for runway 10C to back up a planned visual approach.
However, the crew reported they were unable to receive the ILS identifier. The captain attempted to troubleshoot by reloading the approach in the FMC and manually tuning the frequency. When the issue could not be resolved, the crew elected to continue visually.
The captain advised the tower they were on a visual approach to runway 10C and received landing clearance for 10C. Despite that, the aircraft was aligned with parallel runway 10L and touched down there instead.
In its final report, the National Transportation Safety Board determined the probable cause was the flight crew’s misidentification of the intended landing runway due to planned continuation bias—an unconscious tendency to persist with an original plan despite cues that conditions have changed.
Investigators found that while intercepting the ILS for runway 10C, the correct localizer frequency of 108.95 MHz was tuned into the Nav 1 radio for about four seconds. It was then changed to 108.4 MHz, while Nav 2 was set to 113.0 MHz for the remainder of the flight. With neither radio properly tuned to the ILS for 10C, the crew lacked electronic confirmation of runway alignment.
The NTSB concluded that task saturation and the commitment to continue the approach visually contributed to the crew’s inability to effectively process available information. As workload increased, cues that might have signaled the misalignment were not recognized.
The investigation also scrutinized air traffic control actions. A Federal Aviation Administration mandatory occurrence report indicated the tower controller noticed the alignment error but coordinated with the runway 10L controller to allow the aircraft to land there, as no traffic conflicts were present. The NTSB found this response contrary to FAA directives, stating that the controller failed to notify the crew of the incorrect alignment or issue instructions to prevent the wrong-runway landing. Investigators concluded that timely intervention likely would have averted the event.
The flight landed without injuries or damage, but the case stands as a clear example of how human factors—both in the cockpit and the control tower—can combine to defeat multiple layers of safety. Even in clear conditions at one of the world’s busiest airports, a brief lapse in verification and communication was enough to send a jet to the wrong strip of pavement.
