LONDON -- Four environmental activists climbed atop a plane at London's Heathrow Airport on Monday and unfurled a banner protesting climate change.
Greenpeace said the activists walked across the tarmac and climbed onto the British Airways Airbus A320 after it landed on a domestic flight from Manchester in northern England.
The two men and two women wrapped a banner around the tail fin reading: "Climate Emergency - No Third Runway."
Greenpeace opposes plans for a third runway at Heathrow, Europe's busiest airport.
Heathrow operator BAA PLC said the four protesters were arrested after about 90 minutes and taken to the airport's police station. The airport operator called the protest "unlawful and irresponsible" and said it was investigating the security breach.
The airport was operating normally Monday.