No charges will be laid against the American passenger whose allegedly verbally aggressive, racist behaviour ended with a New Year's Day San Francisco-bound flight from Sydney being diverted to Auckland.

Passengers have told media the man was angry at having to sit in a seat between two people of Indian or Pakistani descent who talked over him.

He was abusive to crew for a prolonged period, his language was profane and at one point he spent 20 minutes in the bathroom.

Passenger Neil Kay posted on Facebook that the passenger was a "misogynistic, homophobic bigot" who verbally harassed "kind passengers" and physically threatened the wonderful United Airlines' flight crew.

Flight UA870 was near Tonga when it was diverted to Auckland.

Immigration New Zealand said the American national was refused entry to New Zealand as he did not meet entry and border requirements.

He is in police custody while arrangements are made for him to board a flight to the United States.

The 252 passengers were put up in hotels as the cabin crew and pilots got enough rest, before the flight took off more than 24 hours later, last night.

Sources said the disruption could cost the United Airlines around $150,000.

The delay means passengers will reach their destinations two days later than planned.