A United Airlines plane headed to China had to divert back to California hours into the flight because one of the pilots forgot their passport.The flight had taken off from Los Angeles and was headed to Shanghai on Saturday with 257 passengers and 17 crew members on board, the airline said.United said they were two hours into the flight when the plane had to turn around and head back to the U.S.RELATED STORY | Heathrow to resume flights after fire cut power to Europe's busiest airportThe plane landed in San Francisco, and a new crew took over hours later.Ultimately, the flight landed in Shanghai six hours behind schedule.NBC News reported that the passengers were given meal vouchers and compensation. ...read more read less