• A United Airlines flight turned back to Newark, New Jersey, after 90 minutes.
• It's the latest example of a flight to nowhere — when flights return to their origin.
• Passengers eventually made it to London 12 hours later than scheduled.

United Airlines passengers faced a 12-hour delay after their transatlantic trip became a flight to nowhere.

Saturday's flight from Newark, New Jersey, to London was in the air for about 90 minutes when it U-turned just off the coast of Nova Scotia, according to data from FlightAware.

The flight-tracking website shows that after landing back in New Jersey at about 2:30 a.m. ET, the Boeing 767 didn't take off again for nearly five more hours.

Flight UA940 ultimately made it to London Heathrow at 7.29 p.m. local time on Sunday — 12 hours and 5 minutes after it was initially scheduled.

In a statement shared with Business Insider, a United Airlines spokesperson said the flight returned to Newark "to address a disruptive passenger."

The statement added that law enforcement removed the passenger before the flight continued to London that morning.

One Reddit user who said they were on the flight said the plane turned around after a business-class passenger threatened the aircraft's security.

They added that the delay at Newark was compounded by the flight crew reaching their maximum time on the clock, so new staff had to be brought in from standby.

The Port Authority of New York and New Jersey didn't immediately respond to a request for comment sent by BI outside US working hours.

Returning all the way to Newark rather than landing at a nearer airport in Canada may initially seem a strange decision, but so-called flights to nowhere aren't uncommon. Going back to an airline's hub airport usually means it's simpler to reroute passengers and solve any issues.

There have been several flights to nowhere in recent weeks.

Last month, a Delta Air Lines plane turned back over the coast of Newfoundland after the crew observed a potential engine issue.

Then, a KLM flight U-turned over the Atlantic Ocean and headed back to Amsterdam in a four-hour flight to nowhere as a precaution because of a technical malfunction.

• A Delta Air Lines Boeing 767 U-turned before crossing the Atlantic on November 24.
• Delta said the flight crew observed a potential engine issue and returned to JFK Airport.
• The 212 passengers departed again some 12 hours after they first took off.

Hundreds of passengers endured a five-hour flight to nowhere as their Delta Air Lines plane turned back.

The Boeing 767 left New York's JFK Airport for Edinburgh, Scotland, at about 10 p.m. ET on November 24.

FlightAware shows that Flight 208 had just reached the Atlantic Ocean when it turned back over the coast of Newfoundland.

Delta said the flight crew observed a potential engine issue and followed established procedures to return to JFK.

The 767 landed back in New York at about 3 a.m., some five hours after departing.

Delta said 212 passengers and 11 crew members were on board. Passengers were given accommodations and meals before leaving New York again at 10 a.m., about 12 hours after their initial departure.

"Delta apologizes to our customers for the delay in their travels and we appreciate their patience," the airline said in a statement shared with Business Insider. "Nothing is more important than the safety of our customers and people."

It's not the only example of a flight to nowhere in recent weeks.

On Sunday, a KLM Boeing 777 U-turned over the Atlantic, leaving passengers with a four-hour flight to nowhere.

In late October, a British Airways Boeing 777 that experienced a problem over the Atlantic turned back to London and landed at Heathrow nine hours after takeoff.

For carriers flying over the Atlantic, returning to the airport is often the best decision when something goes wrong: It's typically simpler for airlines to reroute passengers and fix planes back at their hub airports than abroad.