United Airlines Jets Cleared for Near-Simultaneous Takeoff in United States: San Francisco ATC Timing Error Triggers Parallel Departure Concern

In the United States, aviation safety protocols are built upon precision, coordination, and constant vigilance. Yet even within one of the world’s most advanced air traffic systems, brief lapses in timing can create situations that demand immediate corrective action. Such a moment unfolded at San Francisco International Airport (SFO) in California, where two United Airlines aircraft were cleared for departure on parallel runways within seconds of each other.

Shortly after midnight on January 24, 2026, what was expected to be a routine set of departures toward Houston and San Jose, Costa Rica developed into an unusual operational scenario. A controller misjudged the time required for a widebody jet to enter the runway, and nearly overlapping takeoff rolls followed. Although no collision risk ultimately materialized, the incident drew attention due to the rare sequence of simultaneous clearances and the swift adjustments that were required moments after liftoff.

The event has since been viewed as a reminder of the human element that continues to underpin air traffic control across the United States and globally, including countries such as Costa Rica, where international connections depend on seamless coordination.

Late-Night Operations at San Francisco International Airport

The situation occurred just after midnight at San Francisco International Airport (SFO), one of the busiest gateways on the West Coast of the United States. During late-night operations, traffic volumes are typically lower than peak daytime hours, yet parallel runway procedures remain complex and require precise timing.

Two United Airlines flights were preparing for departure:

• United flight UA2621, operated by a Boeing 777-200ER, scheduled to Houston IAH in the United States
• United flight UA2312, operated by a Boeing 737 MAX, scheduled to San Jose SJO in Costa Rica

UA2621 was cleared for takeoff from Runway 1R. Due to taxiway geometry and the size of the Boeing 777-200ER, additional time was required for the aircraft to properly align on the runway centerline before initiating its takeoff roll.

Shortly thereafter, UA2312 was instructed to line up and wait on Runway 1L, which runs parallel to 1R. Approximately 30 seconds later, takeoff clearance was issued for the Boeing 737 MAX as well.

Because the widebody aircraft was still entering position, both jets began accelerating for departure at nearly the same time, resulting in reduced spacing between the two parallel departures.

How the Timing Misjudgment Occurred

Parallel runway operations are common at major airports in the United States, including SFO. However, these procedures depend heavily on accurate assessments of aircraft positioning and rollout timing.

In this case, the controller appears to have underestimated the time needed for the Boeing 777-200ER to taxi into full takeoff position. Larger aircraft often require additional seconds to align properly due to wingspan, turning radius, and runway entry angle.

Meanwhile, the Boeing 737 MAX was already positioned on the adjacent runway. Once clearance was given, it was able to begin its takeoff roll almost immediately.

As a result, both aircraft accelerated nearly in tandem, despite identical routing instructions that would initially place them on similar departure paths.

Immediate Corrective Action After Liftoff

Once both aircraft became airborne, insufficient departure spacing was recognized. Prompt corrective action was taken by the controller to restore safe separation standards.

New vectors were issued to one of the flights to ensure adequate horizontal spacing. Instead of following the originally planned SSTIK departure route, a modified heading was assigned shortly after departure.

After being transferred to departure control, one of the flight crews sought clarification regarding the unexpected routing change. Confirmation was provided that spacing adjustments were necessary due to the earlier sequencing issue.

Despite the urgency reflected in the revised instructions, cockpit operations were reportedly conducted in a calm and professional manner. Standard separation was restored quickly, and both flights continued safely to their respective destinations in Houston, United States, and San Jose, Costa Rica.

No injuries, damage, or lasting operational disruptions were reported.

The Human Element in Air Traffic Control

Air traffic control systems in the United States are supported by advanced radar tracking, automation tools, and strict procedural safeguards. However, final decisions regarding sequencing and clearances continue to rely heavily on human judgment.

Controllers must monitor aircraft movement, runway occupancy, taxi speeds, departure routing, and weather conditions simultaneously. Even during off-peak hours, multiple aircraft may be managed within a short timeframe.

Midnight operations can introduce additional human factors, including fatigue and reduced staffing levels. In such environments, minor timing miscalculations may occur despite established safeguards.

In this instance, the defining safety feature was not the initial misjudgment but the rapid recognition of the developing spacing issue and the swift issuance of corrective vectors.

Why No Collision Risk Materialized

Although the departures occurred nearly simultaneously, the aircraft were operating on parallel runways with established lateral separation. Standard departure procedures are designed with layered safety measures that allow controllers to intervene quickly if spacing becomes insufficient.

Once airborne, aircraft can be separated vertically, laterally, or through heading adjustments. That flexibility enabled the controller to correct the situation before any hazardous proximity developed.

The event has therefore been characterized less as a near-collision scenario and more as a procedural deviation that required immediate adjustment.

Flights proceeded without further complication, and passengers traveling domestically within the United States and internationally to Costa Rica were not significantly impacted.

Broader Context of U.S. Aviation Oversight

Incidents involving runway timing or spacing are closely monitored within the United States aviation system. The Federal Aviation Administration places significant emphasis on runway safety initiatives, controller training, and fatigue mitigation.

San Francisco International Airport, like other major hubs in California and across the country, operates under stringent federal oversight. Parallel runway operations are routinely conducted safely each day, supporting domestic and international connectivity.

The presence of overlapping clearances in this case has drawn attention because of the unusual sequence in which simultaneous authorizations were later questioned by the controller. However, the swift recovery reinforced the resilience built into the system.

Internationally, aviation authorities in countries such as Costa Rica depend on similar coordination standards when receiving inbound flights from the United States. Seamless transitions between departure and arrival airspace require consistent adherence to spacing protocols.

Operational Lessons and Professional Handling

The incident underscores how critical precise timing is in parallel runway environments. Even minor miscalculations regarding runway entry can temporarily narrow departure spacing.

At the same time, the event highlights the professionalism of both controllers and flight crews. Clear communication, rapid situational awareness, and decisive vector adjustments ensured that safety margins were restored within moments.

No lasting operational consequences were reported. Both United Airlines aircraft continued on schedule, and airport operations resumed normal sequencing shortly afterward.

The episode stands as a case study in how layered aviation safety systems function when unexpected timing issues arise. Rather than demonstrating systemic failure, it illustrated how rapid correction mechanisms maintain safety even when human error occurs.

Bottom Line

Two United Airlines flights departing San Francisco International Airport in the United States began near-simultaneous takeoff rolls after a controller underestimated runway entry timing during parallel operations.

Corrective vectors were issued immediately after liftoff, safe separation was restored, and both flights continued to Houston and San Jose, Costa Rica without further incident.

The event serves as a reminder that while aviation systems rely heavily on human coordination, built-in safeguards and professional response remain central to maintaining safety across the United States and international airspace.

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