UNITED Airlines Flight UA914 declared a mid-air emergency and landed in London earlier this afternoon.

The flight, heading to Washington, left Paris at 12:24pm (local time).

It was scheduled to arrive in Washington at 15.05pm.

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Flight UA914 was holding at 17,000ft and landed safely at Heathrow.

United Airlines released this statement: "The aircraft landed safely at 1.38pm local time.

"Our maintenance team is currently inspecting the aircraft. We are making arrangements for our customers to complete their journeys.  We apologize to our customers for the inconvenience caused."

It is believed an issue with the air conditioning vents caused the emergency landing.