303 passengers went on an 8-hour flight to nowhere following a security threat

• Hundreds of Air India passengers went on an eight-hour flight to nowhere this week.
• The plane turned back to Mumbai after about four hours when the airline detected a security threat.
• It marks Air India's second flight to nowhere incident in less than a week.

Hundreds of Air India passengers went on an eight-hour flight to nowhere on Monday night after the airline detected a security threat.

Data from Flightradar24 shows that Monday's flight from Mumbai's Chhatrapati Shivaji Maharaj International Airport Mumbai to New York's John F. Kennedy International Airport made a U-turn over the Azerbaijan-Armenia border — a little over four hours into the journey.

The flight to nowhere lasted about eight hours and 20 minutes in total. A direct flight from Mumbai to New York usually takes just under 16 hours.

In a statement, Air India said the diversion was because a "potential security threat was detected" during the flight.

"After following the necessary protocols, the flight air-returned to Mumbai, in the interest of the safety and security of all on board," the statement said, adding that the Boeing 777-300 underwent mandatory security upon landing.

The plane landed back in Mumbai at 10:25 a.m. local time, per Flightradar24.

The airline told Live from a Lounge that 322 people, including 19 crew members, were on board. Air India said the flight was rescheduled to the following day and passengers were offered hotel accommodation, meals, and other assistance.

Air India did not respond to a request for comment from Business Insider.

It was the second flight to nowhere for Air India in less than a week.

On March 7, an Air India flight returned to Chicago after a nine-hour journey when most of the plane's bathrooms stopped working. The airline's investigation found that bags, rags, and clothes had been flushed down the toilets, blocking the plumbing.

Flight diversions, particularly those that return to the departure airport, can be costly for airlines and annoying for passengers, but they are often necessary for safety reasons.

These decisions are usually made on a case-by-case basis, but some carriers, such as American Airlines, have their own automated tools to help dispatchers and other airline workers determine whether a U-turn is necessary.