Among these special constructions are the bookkeeping machines planned by I.B.M. for air transport corporations. One of the problems of these companies is to see to it that their planes always carry passengers to their full capacity, that all their seats are occupied - but that no reservations are made for more than the complete number of seats. Moreover, the weight of baggage must not exceed a certain maximum. But as the airlines have agencies in London, Paris, Berlin, Madrid, Rome and many other places, all of which sell tickets for the same flight to New York, for instance, it is impossible for the people at the ticket counters in the various cities to know exactly whether there are still seats vacant in any particular plane. If a customer is turned away unnecessarily by a ticket seller, told that the airline is sorry but a certain flight is fully booked up, there will be trouble with the management. If he is sold a ticket anyway, and the plane turns out to be full already, there will be trouble with the customer. Today, such problems are solved electronically by a computer in the head office of the airline, and connected to each branch agency by teleprinter lines. Miss Svensson of Stockholm, who wants to fly from her home town to New York, names the day of departure she prefers. The clerk at the counter in Stockholm types the desired flight on his teleprinter. A second later the computer at the central office informs her whether there is a seat still free. If there is, Miss Svensson's name, address and telephone number are typed into the teleprinter. Her seat for the flight is booked. Miss Svensson gets her ticket, and the computer at the head office reduces the number of vacant seats by one.
If Miss Svensson changes her mind and decides later that she would rather take another plane, if she falls ill and cannot fly at all, if the flight cannot take place because of engine trouble so that all the passengers must be turned over to another airline - the computer arranges everything.
While we are on the subject of air transport: another big problem in air travel is safety. It becomes more and more difficult to direct the machines landing at or starting from an airport so that accidents are ruled out Each machine is assigned a certain route and height (a "pattern"). Delayed arrivals must be fitted in, and if there is an accumulation of planes waiting to land, it often happens that several of them must spend some time circling the skies above the airfield, exactly at the heights allocated to them.
The problem, in fact, is essentially the same as in a big railway station at which a train arrives every minute or so - but it is much more complicated. For in the air there are no rails on which the vehicles follow a precisely planned route, even at night or when it is foggy. There are no signals, only radar and radio. And, worst of all, planes cannot simply stop in mid-air as a freight train does when it is confronted with a red light They must always be kept moving. To help you imagine what it means to keep a dozen cruising planes well away from one another over an airport in misty weather, and to organize landings and take-offs - take a look some time at a blindfolded juggler on a tightrope keeping seven coffee cups and a sugar bowl in the air.
In air navigation these jugglers are seated in a tower high above the airport, and many of them at hot-under-the-collar moments must undoubtedly feel that they would give the world for a dependable computer that would relieve them of some of their work - say, the observation and control of the circling planes. Efforts are being made to develop such special computers and it will probably soon be possible to put them to work.