I understand that, in American English usage, 'persons' is often used to indicate a number which can be counted - often in a legalistic way - and 'people' where a large or uncounted number is involved. Thus, they might write: "This elevator is designed to carry no more than fifteen persons."
Such a sign then covers the business in whose premises the elevator is from having to pay damages if the wretched thing crashes with sixteen people aboard! We sometimes do the same in such circumstances.
However, both in the USA and Britain, "people" is becoming far more common im virtually any situation.