Two regional passenger jets, both Embraer 175s, came within 300 vertical feet of each other during their approach to Greensboro/Piedmont Triad International Airport (GSO) on Sunday, September 7, 2025, shortly before 11:00 p.m. local time. An air traffic control conflict alert sounded, prompting immediate action by controllers and pilots to prevent a closer encounter.
The incident involved American Eagle flight AA3754 from Miami, operated by Envoy Air, and United Express flight UA5503 from Denver, operated by SkyWest. This near-miss highlights critical safety protocols in air traffic management and the importance of rapid response systems.
Key Takeaways
- Two regional jets approached Greensboro within 300 vertical feet.
- An air traffic control conflict alert system activated.
- Pilots and controllers acted quickly to increase separation.
- The incident involved American Eagle and United Express flights.
- Standard separation rules require at least 3 nautical miles laterally during final approach.
Details of the Near-Miss Event
On the evening of September 7, 2025, an air traffic controller was managing both American Eagle flight AA3754 (Envoy 3754) and United Express flight UA5503 (SkyWest 5503) for landing on runway 5R at Greensboro. Initial instructions from air traffic control (ATC) involved speed adjustments for SkyWest 5503, first at 210 knots and then 170 knots, along with clearance for an RNAV (GPS) approach, including a directive to "cross COSIS at or above 3,000 feet."
Meanwhile, Envoy 3754 reported having the runway in sight. It was then cleared for a visual approach to runway 5R with the instruction to "keep it as fast as you can as long as you can." Following this, Envoy 3754 was switched to the tower frequency.
Important Air Traffic Control Terms
- RNAV (Area Navigation) Approach: A type of instrument approach that allows aircraft to fly a precise path using satellite navigation (GPS) or other navigation systems, rather than ground-based beacons.
- Visual Approach: An approach where a pilot proceeds visually to the airport, maintaining visual contact with the ground and/or other aircraft, often after being cleared by air traffic control.
- Conflict Alert: An automated radar system that warns air traffic controllers when two or more aircraft are projected to violate minimum separation standards.
Controller Instructions and Pilot Response
A few miles after Envoy 3754 was cleared for visual approach, the controller asked SkyWest 5503 if they had Envoy 3754 in sight. The controller instructed SkyWest 5503 to follow the preceding traffic, adding, "if you can’t, I’ll break you out." At this point, SkyWest 5503 was still on an instrument approach (RNAV 5R) and had not been explicitly cleared for a visual approach or instructed to maintain visual separation.
Shortly after these instructions, a conflict alert sounded on the radar screen. This alert signals that minimum separation standards between aircraft were being violated or were imminent. SkyWest 5503's pilots immediately requested a "breakout," meaning they asked to deviate from their current approach path to avoid the conflict. The controller promptly directed SkyWest 5503 to turn away and climb, effectively re-sequencing the aircraft to ensure safe spacing.
"The radar conflict alert tone fired. SkyWest quickly requests a break‑out; the controller turns and climbs them, re‑sequences, and the arrivals are spaced out."
Separation Standards and Safety Margins
At their closest point, the two aircraft were only 300 vertical feet apart. While lateral separation was approximately 2 miles, this combination triggered the conflict alert. In terminal radar operations, air traffic controllers typically must maintain a minimum of 3 nautical miles of lateral separation during the "turn-on" to final approach. A near mid-air collision is generally defined as proximity of less than 500 feet, or any instance where a pilot reports a collision hazard.
The incident represented a significant reduction in the expected safety margin. The primary responsibility for maintaining proper separation until aircraft are safely established on approach, or visual separation is explicitly applied, rests with approach control.
Air Traffic Control Responsibilities
Air traffic controllers play a crucial role in maintaining safety and efficiency in the skies. Their responsibilities include:
- Sequencing aircraft for arrival and departure.
- Maintaining minimum separation standards between aircraft.
- Issuing clearances and instructions to pilots.
- Monitoring radar and responding to alerts.
- Providing essential information like weather updates and traffic advisories.
Effective communication and adherence to established protocols are vital for preventing incidents.
Analysis of the Incident
The core issue in this incident appears to be the lack of a clear instruction regarding visual separation for SkyWest 5503. The controller asked SkyWest to follow Envoy without explicitly switching them from an RNAV instrument approach to a visual approach, nor did they issue the standard instruction to "maintain visual separation." When visual separation is not explicitly in force, the air traffic controller remains responsible for maintaining radar separation.
The sequence of events suggests that the controller attempted to keep Envoy 3754 ahead with the instruction to "keep it fast." However, telling an aircraft already cleared for an RNAV approach to "follow that traffic" without a clear visual approach clearance and a "maintain visual separation" instruction deviates from standard procedure.
Key Data Points
- Date of Incident: Sunday, September 7, 2025
- Time: Shortly before 11:00 p.m. local time
- Location: Greensboro/Piedmont Triad International Airport (GSO)
- Aircraft 1: American Eagle AA3754 (Envoy Air Embraer 175)
- Aircraft 2: United Express UA5503 (SkyWest Embraer 175)
- Minimum Vertical Separation: 300 feet
- Lateral Separation: Approximately 2 miles
Why Did This Happen?
While 2.5-mile finals are sometimes permissible, especially at non-hub airports, they are typically used only when specific conditions align. These conditions include appropriate equipment, favorable weather, a suitable mix of aircraft, efficient runway exits, and adequate staffing. Such close spacing is usually reserved for situations where high demand justifies fitting in extra arrivals.
In this case, Greensboro is not a highly congested airport like New York LaGuardia. The decision to attempt such close sequencing without clear adherence to established visual separation protocols consumed the safety margin without an apparent operational necessity. The conflict alert system performed its function by warning controllers of the impending issue, and the SkyWest pilots' decision to request a breakout was critical in resolving the situation safely.
Preventative Measures and Future Outlook
This incident underscores the importance of strict adherence to air traffic control procedures and clear communication between controllers and pilots. While automation, such as the conflict alert system, provides a vital layer of safety, human judgment and procedural compliance remain paramount.
Investigations into such incidents typically review controller actions, pilot responses, and communication logs to identify any procedural deviations and implement corrective training or policy adjustments. The goal is to learn from near-miss events to prevent actual accidents and continuously improve air safety protocols.
The quick actions taken by both the air traffic controller and the SkyWest flight crew after the alert sounded successfully prevented a more serious outcome. This event serves as a reminder of the complex and critical work performed daily by air traffic controllers and pilots to ensure the safety of air travel.
