A pilot begins each international flight (or any flight) by getting all the pertinent facts and applying them correctly. In some countries computers play a large part in this preparation. Of a possible dozen routes of flight, a computer can automatically take into account the aircraft’s capabilities against the weather, types of clouds, winds aloft, altitudes, and dis tance to the final destination, to produce a flight plan or several possible courses from which the aircraft commander can choose. Without a computer, all the variables of flight must be taken into account and figured by hand. No matter which method is used, the pilot should scrupulously review the details in order to decide the best route of flight. He or she will then go to the weather forecaster for a briefing.The forecaster needs to know the type of aircraft the pilot is flying, the estimated time of departure (ETD), the proposed route and flight altitude, cruising airspeed, estimated time of arrival (ETA) and any other information which will assist in visualizing this particular flight. When the briefing is over, the pilot should have received the following flight informa tion: weather for takeoff and climb, forecast weather en-route, forecast weather for destina tion and alternates.The pilot now applies this important information to the proposed flight in order to judge what to expect at the point of takeoff, en-route, and at the destination or alternates. As a rule, if the departure is delayed longer than one and one half hours, the weather is re-checked. In addition to checking the weather, a pilot also checks the NOTAMs. Other members of the crew also play a vital role in assembling the hundreds of facts and details needed for the flight. The copilot figures the weight and balance of the aircraft by computing the position of either the passengers and their baggage or the cargo the plane is carrying. Computations are also made for fuel consumption, flight time endurance, and other details needed in preparation and filing of a flight plan. Out on the flight lines - hours before the arrival of the flight crew - other people have been deeply involved in the many, many details involved in launching a modern jet aircraft. The plane is fuelled. A crew chief or team of mechanics check the plane from the pressure in its tires to the oil in its engines. The purpose of the flight plan is to relay the desires of the pilot to the air traffic controller. IFR flight plans are normally filed in base operations at least thirty minutes prior to proposed takeoff, so that they can be transmitted to the appropriate air traffic service. Flight plans can also be filed by radio if no other means are available-except for those involving buffer zones or an ADIZ (air defense identification zone).2.To judge what will happen to the proposed flight, the pilot should know （ ） ．