An Air New Zealand flight from Los Angeles to London set off an emergency signal last night.
Flight NZ2, a Boeing 777, set off an emergency "squawk" at 8.24pm (NZ time) after reportedly suffering hydraulic problems.
Flightradar24.com revealed the emergency beacon was activated last night, about an hour before it was due to touch down at London's Heathrow Airport.
Soon after, a UK air traffic controller said the plane was suffering hydraulic problems.
Jon Wornham posted on Twitter the plane would need a long final approach if it was having hydraulic problems.
The Flightradar24.com website issued a second emergency signal at 9.22pm as the plane was over London.
Postings on a social networking site indicated the plane was travelling faster than usual on its approach to Heathrow but still managed to land safely just after 9.30pm.
A statement from Air New Zealand said Flight NZ2 landed without incident at London Heathrow following a minor technical incident which resulted in "some loss of hydraulic pressure".
"The aircraft was travelling between Los Angeles and London with 330 persons on board. No emergency was declared."