From the moment an airliner takes off to the moment it lands,every movement is watched on radar screens.Air traffic controllers tell the pilot exactly when to turn,when to climb,and when to come down.The air traffic controllers around a busy airport like London-Heathrow may deal with 2,500 planes a day.Not all of them actually land at the airport.Any plane that flies near the airport comes under the orders f the controllers there.Even a small mistake on their part could cause a terrible accident.

从一架客机起飞到降落的每个动作都通过雷达屏幕监控，航空管制员告诉飞行员什么时候转弯、什么时候向上爬、什么时候降落。像在伦敦希思罗这样繁忙的机场，航空管制员一天要处理大约2500架次飞机的起落（问题）。飞近该机场的任何一架飞机都要接受该站的航空管制员的指挥，即使是一个微小的失误都可能导致一个可怕的后果。