United Airlines Flight UA770, a Boeing 787-9 Dreamliner en route from Barcelona to Chicago, was diverted to London Heathrow on May 27, 2025, due to a cabin pressurization issue. Approximately 90 minutes into the flight, the crew detected a malfunction in the pressurization system, prompting them to declare an emergency by activating the universal squawk code 7700, signaling a serious situation requiring immediate attention. The aircraft descended rapidly to a lower altitude, and oxygen masks deployed as a precautionary measure. The decision to land at Heathrow was based on its proximity, available facilities, and emergency response capabilities. The aircraft landed safely without incident, and no injuries were reported among the 257 passengers and 12 crew members. United Airlines initiated a thorough inspection of the aircraft, and the airline is cooperating with aviation authorities to determine the exact cause of the pressurization malfunction.