During the takeoff roll on runway 16, the crew initiated a high-speed rejected takeoff at approximately 143 knots. The aircraft stopped beyond the intersection with runway 28 with several main tires deflated. According to Swiss media outlet Tages-Anzeiger, the flight deck crew initially informed air traffic control that they could vacate the runway and requested time for checklist procedures. However, emergency responders were already en route and instructed them to remain in position.
Zurich Airport authorities confirmed that the aircraft was evacuated shortly afterward and later towed from the runway nearly four hours after the incident. The cause of the rejected takeoff is currently unknown. United Airlines confirmed to local media outlet "20 Minuten" that there was a "technical issue" before departure. A United spokesperson stated, "We are working to rebook customers on alternative flights to get them to their destination as quickly as possible."
Rejected takeoffs are standard aviation safety procedures but are operationally unusual at such speeds as seen in Flight UA12. Flightradar24 data showed that the aircraft reached speeds above V1—the maximum speed at which a safe rejection can occur—indicating exceptional circumstances since only about 2% of rejected takeoffs happen above 120 knots.
Reasons for rejecting a takeoff often include engine failures or system faults among others; however, airline procedures may vary by operator standards.
Several incidents involving major airlines have occurred recently regarding rejected takeoffs due to various reasons including technical issues and bird strikes.