The Portuguese Government just announced the plans for the major public constructions including decisions about the high-speed train, motorways andthe new Lisboa Airport.
Some years ago a study was conducted to determine where could a new airport for Lisboa be built. There were two major sites/options : Ota or Rio Frio. Ota (LPOT) was alraedy used by the Portuguese Air Force some years ago and still has a runway and other facilities which are used once or twice a year, Rio Frio is located south of Tejo River and the major problem with this location was environmental - the location is used by several species of birds for nidification (?).
There are still many people (actual Mayor of Lisbon included) who want to keep the airport where it is and use one of the near military bases (Alverca-LPAR, Montijo-LPMT or Sintra-LPST) for cargo, charters and low-cost airlines...
Even with the recent construction works (RET, ...) Lisboa Airport his - according with the study - reaching its maximum capacity.