Heathrow expanison
(File photo) The United Airlines plane was forced to change route and land in Heathrow Eddie Keogh/ Reuters

A United Airlines flight from Germany to the US was forced to make an emergency landing at Heathrow Airport after passengers complained of feeling nauseous and dizzy.

The flight from Munich to Newark was diverted to the London airport after people on board complained feeling light headed during the flight.

The Boeing flight UA-31 was around 180 miles away from London when it was forced to changed its route.

An investigation has been launched to determine what caused the passengers to become unwell and the plane has been removed from service.

According to Aviation Herald, one passenger was removed from the flight after emergency services boarded once the plane landed safely on the runway at Heathrow.

All remaining passengers were eventually safely taken off the flight to undergo medical checks before being rebooked onto to other flights.

One of the passengers on board the flight, Pete Teoh, tweeted updates from inside the plane, including the moment emergency services came to check on people feeling unwell.

Teoh added that he "felt fine" during the flight and did not feel the same illness as some of the other passengers.

An incident report on the Aviation Herald stated: "United Boeing 767-300, registration N653UA performing flight UA-31 from Munich (Germany) to Newark,NJ (USA), was enroute at FL320 about 180nm west of London,EN (UK) when the crew decided to turn the aircraft around and divert to London Heathrow after a number of passengers complained about feeling light headed and sick with nausea. The aircraft landed safely in Heathrow about 45 minutes later.

"Medical Services entered the aircraft and checked a number of passengers, one passenger was taken off the aircraft. Some time later all passengers disembarked and underwent medical checks.

"The airline reported the aircraft was removed from service, the passengers were rebooked onto other flights. Emergency services attended to the aircraft and examined the aircraft, all passengers disembarked and were examined by doctors.

"The cause of the illnesses is under investigation."