New Delhi, March 25 -- Flight delays are not uncommon, and so aren't emergency landings. However, a fight returning to the source after spending hours in the air still raises an eyebrow.

After Air India's 10-hour mid-air saga, this time, a United Airlines flight from Los Angeles to China took an unexpected U-turn.

According to a CNN report, the China-bound flight was in the air for 2 hours before it had to return to Los Angeles because of a "blunder". This U-turn caused Shanghai passengers to experience a 6-hour delay overall.

Only 2 hours after the flight had left Los Angeles, the crew discovered that one of the pilots had boarded the flight without their passport.

"The pilot did not have their passport onboard," United Airlines was ...