WELCOME TO HEATHROW

London's Heathrow is the busiest international airport in the world. It handles over 350,000 international flights every year - about 41 million passengers. Around 54,000 people work at Heathrow, roughly the population of a country town.

Huge machines wash the airport's three runways and clear away the oil left by jet engines. Burst tyres can cause a crash, so special trucks continuously check the runways and pick up any loose pieces of metal.

Birds can cause crashes if they get pulled into the engines, and staff work day and night to keep them away from the runways. Their trucks have loudspeakers which send out bird alarm calls, they also use guns with blank cartridges to frighten the birds away.

In the control tower, 150 air traffic controllers bring the planes in and send them off safely. As a plane comes in to land, it normally keeps a distance of five or six kilometres from the planes in front and behind, but in the case of large jumbo jets, the distance behind has to be 10 kilometres. The air turbulence behind these planes can send a small plane out of control.

Near the centre of the airport is the police station. It has a huge picture board of known world terrorists, 14 dogs that can smell drugs and 300 police officers. There is an aircraft alert almost every day. This happens every time an aircraft lands with one engine shut down or if the pilot cannot lower the plane's wheels. The emergency services can lay a carpet of foam on the runway in less than four minutes.

The Medical Centre has eight nurses and three doctors always on standby. The most common illness is heart attack. Every year about 30 people die in this way while travelling to or through Heathrow.

Because of the noise, only a few flights are permitted between midnight and six in the morning. So during the night Heathrow Airport has its most welcome visitor of all - silence.