UA2664 - Smoke in Cabin Emergency Return

United Airlines Flight UA2664, operating a Boeing 737 MAX-9, departed San Francisco International Airport (SFO) bound for Baltimore/Washington International Airport (BWI) on September 2, 2025. During the flight, the flight crew detected smoke in the cabin compartment. Following standard safety protocols, the pilots immediately decided to return to San Francisco. The aircraft made a safe emergency landing at San Francisco International Airport at approximately 10:40 AM local time on Tuesday, September 2, 2025. All passengers and crew were safely accommodated with no injuries reported. The aircraft was subsequently grounded for investigation and maintenance. The FAA opened an investigation into the smoke incident. This incident occurred amid ongoing scrutiny of Boeing 737 MAX aircraft following previous safety issues. The NTSB has previously issued urgent safety recommendations regarding potential smoke entering cockpit/cabin due to engine oil system damage in Boeing 737 MAX aircraft. CFM engines on 737 MAX have a load reduction device that can damage oil systems after bird strikes, potentially causing smoke in cabin.