Your gateway in and out of Lisbon is Portela Airport, or Aeroporto da Portel, located within the city boundaries; it's the main hub of TAP-Portugal and Portugalia, the country’s top 2 airlines which fly to Europe, Africa and the Americas.
You can fly via TAP-Portugal, the country’s flag carrier, which offers cheap economy class flights to Lisbon; you're only allowed to carry hand luggage which does not exceed 45 in and 13 lbs. Most beverages are available for no extra charge; you can also get blankets, pillows, writing paper, postcards, and games here.
EasyJet, one of Europe’s largest low-cost carriers, offers no-frills and cheap Lisbon flights; this means unassigned seats, no complimentary food, and no connecting flights.
SkyEurope is another budget airline that offers limited routes in Central Europe, including Lisbon; you can also check out bmibaby, a British low-cost airline that services routes in Europe.