This document carries out the theoretical project of extension of the corporate terminal of the Barcelona-El Prat's Airport. This project has two aims: In one hand tries to determine the prognosis of corporate traffic for the airport in an average horizon of design following the indications of the pertinent aeronautical organisms. In the other, use the data obtained to project an extension of the currentterminalbuildingthatfollowfulfillingalltheaeronauticalrulesandthatitcanabsorb the new traffic, as well as place the offices of the companies that operate in the building. Tocarryoutthefirstpoint, theprognosisandthepertinentdiagnostic, asearchofthemost extended methods for the forecast calculation is done. Then which is better for the horizon proposed is chosen and the projection is done. Once we have the results, following the percentages of use of the terminal, the new percentages of use expected for the future are calculated. We analyze if the current building will be able to house all the traffic, and we obtain that it is not, so we propose the extension. In the second part, the part of design of the extension, we analyse the two terrain options available. Once chosen the terrain, we project a smaller continuation of the current terminal. As now there are two terminals joined, we propose to do a separation of fluxes to do even more exclusive the terminal, due to the fact that the passengers will use only the existent terminal, and the new will house new offices where the companies and/or AENA will work. We then design the new spaces to fulfil the new needs. Once done the design, we calculate the structure and the foundation. We opt for a metallic structure. Later on we calculate the cover. Also we calculate the closings because they fulfil the thermal requirements. Finally we do the planning of the work with the use of Gantt's Diagram. This planning is accompanied by an approximated budget of what would cost to carry this project out. Wepresentinthisprojectallthenecessarydocumentstojustifythedesignandcalculation, as well as to carry out his building. The project is presented in an academic field, as a requirement for the obtention of the title of Grau en Enginyeria en Aeronavegaci´o/ Grau en Enginyeria en Aeroports.