1. AIR TRAFFIC CONTROL SYSTEM COMPRISING, IN COMBINATION, A COMPUTER FOR CALCULATING ESTIMATED TIMES OF ARRIVAL OF AN AIRCRAFT, AN INPUT CIRCUIT INCLUDING A TELEPRINTER LINE FOR FEEDING CODED INFORMATION RELATING TO AIRCRAFT FLIGHTS TO THE TRAFFIC CONTROL SYSTEM, SAID INFORMATION INCLUDING THE TIME AT WHICH THE AIRCRAFT IS AT A KNOWN POSITION, CODED INDICATIONS OF THE TYPE OF AIRCRAFT AND THE FLIGHT ALTITUDES, A CODE-CONVERTER CONNECTED TO SAID INPUT CIRCUIT FOR CONVERTING SIGNALS IN A CODE COMPOSED OF SUCCESSIVELY OCURRING CODE ELEMENTS RECEIVED THROUGH THE TELEPRINTER LINE INTO SIGNALS FORMED BY SIMULTANEOUSLY OCCURRING CODE ELEMENTS, A PROGRAMMING ARRANGEMENT CONTROLLING THE SEQUENCE OF OPERATIONS IN THE SYSTEM AND IN THE COMPUTER, A FIRST MEMORY SYSTEM FOR CONSTANT DATA COMPRISING A NUMBER OF MEMORY ELEMENTS OF A FIRST TYPE, EACH ONE OF SAID FIRST TYPE ELEMENTS STORING A PERMANENT REGISTRATION OF DATA APPLYING TO A TYPE OF AIRCRAFT TO WHICH THE RESPECTIVE ELEMENT PERTAINS, CIRCUIT CONNECTIONS FOR CONVEYING CODED INFORMATION FROM THE CODE CONVERTOR TO SAID FIRST MEMORY SYSTEM, MEANS FOR SELECTING ONE OF THE MEMORY ELEMENTS PERTAINING TO A CERTAIN TYPE OF AIRCRAFT, COMPRISED IN SAID MEMORY SYSTEM AND RESPONSIVE TO THE COMBINED ACTION OF SIGNALS RECEIVED FROM THE PROGRAMMING ARRANGEMENT DURING THE INTERVAL DURING WHICH THE PART OF THE CODED FLIGHT INFORMATION INDICATING THE TYPE OF AIRCRAFT IS INTRODUCED INTO THE SYSTEM AND THE CODED SIGNALS INDICATING SAID TYPE OF AIRCRAFT, CIRCUIT CONNECTIONS FOR CONVEYING INFORMATION FROM THE MEMORY SYSTEM TO THE COMPUTER AND MEANS IN THE MEMORY SYSTEM WHICH IN RESPONSE TO FURTHER SIGNALS FROM THE PROGRAMMING ARRANGEMENT SUPPLY THE COMPUTER, BY WAY OF SAID LAST MENTIONED CONNECTIONS, WITH CODED INFORMATION AS TO CONSTANT DATA REQUIRED FOR THE CALCULATIONS EFFECTED IN THE COMPUTER AND VALID FOR THE TYPE OF AIRCRAFT INDICATED BY THE CODED SIGNAL AND SUPPLIED BY THE SELECTED MEMORY ELEMENT, A SECOND MEMORY SYSTEM FOR CONSTANT DATA CONNECTED TO THE COMPUTER INCLUDING A NUMBER OF MEMORY ELEMENTS OF A SECOND TYPE, EACH ONE OF SAID SECOND TYPE ELEMENTS STORING A PERMANENT REGISTRATION OF SUCH DATA AS VALID FOR A ROUTE IN THE AREA IN WHICH TRAFFIC CONTROL IS EFFECTED AND TO WHICH ROUTE THE SAID ELEMENT PERTAINS, CIRCUIT CONNECTIONS FOR CONVEYING CODED INFORMATION FROM THE CODE CONVERTER TO SAID MEMORY SYSTEM, MEANS FOR SELECTING ONE OF THE SECOND TYPE MEMORY ELEMENTS PERTAINING TO A CERTAIN ROUTE, COMPRISED IN SAID SECOND MEMORY SYSTEM, SAID SELECTING MEANS BEING RESPONSIVE TO THE COMBINED ACTION OF SIGNALS RECEIVED FROM THE PROGRAMMING ARRANGEMENT DURING THE INTERVAL DURING WHICH THE PART OF THE CODED FLIGHT INFORMATION INDICATING THE ROUTE TO BE USED DURING THE FLIGHT IS INTRODUCED INTO THE SYSTEM, AND THE CODED SIGNALS INDICATING SAID ROUTE, SIGNALLING CONNECTIONS CONNECTING SAID MEMORY SYSTEM AND THE PROGRAMMING ARRANGEMENT, MEANS IN THE PROGRAMMING ARRANGEMENT WHICH IN RESPONSE TO SIGNALS APPLIED TO SAID SIGNALLING CONNECTION BY THE SECOND MEMORY SYSTEM AS A RESULT OF THE SELECTION OF A SECOND TYPE MEMORY ELEMENT, ADAPT THE PROGRAM OF THE CALCULATIONS CONTROLLED BY THE PROGRAMMING ARRANGEMENT TO THE ROUTE, CALCULATING MEANS IN THE COMPUTER CONTROLLED BY THE PROGRAMMING ARRANGEMENT IN ORDER TO CALCULATE THE ESTIMATED TIME OF ARRIVAL OF THE AIRCRAFT AT VARIOUS POSITIONS ON THE ROUTE FROM THE INFORMATION RECEIVED THROUGH THE INPUT CIRCUIT AND THE INFORMATION RECEIVED FROM SAID MEMORY CIRCUITS, AND AN OUTPUT CIRCUIT TO WHICH CODE SIGNALS REPRESENTING THE RESULTS OF THE CALCULATIONS ARE APPLIED.