An international flight operated by United Airlines, bound for Shanghai from Los Angeles, made an unexpected U-turn mid-flight after the pilot realized he had forgotten his passport. The incident, described as quite embarrassing, forced the Boeing aircraft to return to San Francisco approximately two hours into the 13-hour journey. This mishap marks the second instance within a week where pilots on United flights encountered similar issues, raising concerns about procedures for pre-flight checks. Passengers experienced an unusual detour, prompting discussions about pilot preparedness for international travel.