A man was arrested after it was claimed he had a racist rant onboard a United Airlines flight bound for San Francisco, which led to it being diverted to Auckland.

The New Year's Day flight, which originated in Sydney, was diverted after a passenger failed to listen to crew on Sunday afternoon.

Passengers have recounted the man allegedly going into a verbally abusive, racist rant when two other passengers described as being of Indian or Pakistani descent, seated on either side, talked over him.

A video shared on social media captured the man, after this exchange, yelling at an air attendant who tried to calm him down.

He was heard saying that it would be "cool" if the flight was turned around.

"If you guys treat people right on these things, you see two last names the same don't put someone else in the middle of them," he said. "I'm not yelling ... you want to hear me f****** yelling.

"Do you know how cool it would be to have the aeroplane turned around because of me? You are going to do that? You do that? I'm being so impolite aren't I? Fat ass".

One passenger seated three to four rows in front of him said the situation escalated from there with the man, a Caucasian, turning on the attendants who tried to intervene.

"The rant progressed from cursing Indians to Asians to Muslims to non-whites in general and calling flight crew f****** and fat asses," he said. "He was subdued after the pilot announced the diversion to Auckland.

"When the flight landed in Auckland he was told to co-operate when police removed him or he would face additional charges.

"Passengers took cellphone video of his removal and he called them f****** as he passed them."

Another passenger said the man "exploded into a fit of rage" 40 minutes into the flight.

He said the man then proceeded to launch into "offensive language, racial and sexist slurs" and began to grab soda off the cart and demanded beer.

Another video shows the man, more subdued, being escorted off the plane.

Another passenger described seeing him not long after "making calls, trying to lawyer up".

A police spokeswoman said the man, a 42-year-old foreign national onboard flight UH870, was badly behaved and was arrested on arrival before being referred to immigration.

United Airlines spokeswoman Erin Benson said the flight was diverted because a passenger failed to follow crew instructions.

"Authorities boarded the aircraft when it landed and the passenger was removed from the aircraft."

Benson said all 252 passengers were put up in hotels overnight.

The crew of four pilots and 11 flight attendants had to be given enough time to rest before the plane, a Boeing 787, could take off again today.

She said the airline apologised to all those onboard for the inconvenience.

Benson added the airline would review the incident but was unable to give more details into the specifics of the passenger's actions.

Immigration New Zealand national manager, Border, Senta Jehle, said the passenger was an American national.

"He was refused entry to New Zealand as he did not meet entry and border requirements.

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

Flight UA870 departed Sydney at 1.14pm local time and was near Tonga when it was diverted to Auckland.

It landed about six hours later on New Year's Day evening, thousands of kilometres from San Franciscom, and was expected to depart for its original destination around 3.30pm. However, the Herald understands from one passenger due to leave on the flight there were further delays.

It's understood the aeroplane began boarding shortly after 5pm and took off shortly after 6pm.

Photos on social media show the passengers making the most of the unexpected stop, sharing a glass of wine together and paying kudos to the attendants for remaining calm.