Today, air travel is much safer than driving a car on a busy motorway.But there is the danger that grows every year.From the moment the airplane takes off to the moment it lands,every movement is watched on radar screens.(1)_______________________.The air traffic controllers around the busy airport may handle 1,000 planes a day.Any plane that flies near the airport comes under the orders of the controllers there.Even a small mistake on their part could cause a disaster.Recently, such a disaster almost happened.Two large jets were flying towards the airport.One was carrying 69 passengers and had come from Toronto;the other was carrying 176 passengers from Chicago.(2)_______________________.He ordered one to turn to the right to climb,but he made a mistake.He ordered the wrong plane to do this.So, instead of turning away from the second plane,the first plane turned towards it.15 seconds later, it flew directly in front of the second plane.They avoided each other by the smallest part of a second.(3)_______________________.This is an example of the danger that grows every year.