Recently, a flight from Los Angeles to Tokyo turned around and returned to LAX after it was discovered that an unauthorized passenger was on board. From the LA Times:

A Tokyo-bound flight from Los Angeles that turned back to widespread attention on social media was carrying two brothers, one of whom was not authorized to be on board, the Transportation Security Administration said Wednesday.

The unauthorized passenger had a boarding pass for a United Airlines flight, but boarded the All Nippon Airlines flight with his brother, who had the correct ticket for the flight, said Mike England, a TSA spokesman.


“At the time during the flight, the pilot in command was presented with information about the discrepancy in the passenger manifest. Based on the available information in flight, he made the correct decision to return to LAX,” the airline said in a statement. “ANA supports the decision of the pilot, out of the abundance of caution and safety for the passengers and crew onboard.”

From my armchair, it seems like a drastic step to return all the way to LAX rather than diverting to an airport such as Anchorage or Seattle, or even continuing to Tokyo. I'm aware that under some circumstances, airlines can be fined for bringing passengers to a country who turn out to be inadmissible; but I can't imagine that this fine is greater than the cost of scotching an entire intercontinental flight.* Similarly, it doesn't seem likely to me that the additional expense of a diversion would be less than the cost of returning to LAX.

Turning the flight around for security reasons doesn't entirely make sense to me either. The flight had already been en route for four hours before the error was discovered; the additional risk taken on by continuing or diverting seems minimal given the level of risk the flight was already exposed to by letting the extra passenger on in the first place.

But I'm not an expert in the cost-benefit-risk analyses that go into these decisions. So I ask the experts here: What factors would be considered in making a decision like this, and how did these factors lead to this decision?

*In the end, the extra passenger would probably have been admissible—he had a boarding pass for a United airlines flight from LAX–NRT leaving at the same time—but the crew presumably did not know about this at the time.

closed as primarily opinion-based by Doc, choster, David Richerby, Ali Awan, CGCampbell Dec 28 '17 at 17:37

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

  • I wasn't sure whether this question should go here or in Aviation.SE (or neither), so the mods should feel free to migrate/close it if it's not a good fit here. – Michael Seifert Dec 28 '17 at 15:12
  • I feel that this belongs on Aviation.SE but I'll let the users vote on it – JonathanReez Supports Monica Dec 28 '17 at 15:36
  • I don't think this belongs on StackExchange at all. This question is being discussed on a number of different aviation forums, and the simple answer is nobody but the airline knows. Any answers are going to be speculation, not facts. Marking to close as opinion based, not because the question is, but because the answers will be... – Doc Dec 28 '17 at 16:07
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    VtC as unclear, as I'm not sure how knowledge of the airline's decision-making process in such matters would be helpful to travelers. No one is going to choose flights based on whether, in the event of a gate agent error in boarding an intercontinental flight, a particular airline is going to weigh scheduling implications against labor costs against fuel consumption or whatnot X number of hours into the flight. – choster Dec 28 '17 at 16:42
  • The exact sequence of events has yet to be revealed. – Johns-305 Dec 28 '17 at 18:21