The nearest airport is in Humberto Delgado Airport (LIS), located 1.2 mi (1.9 km) from the city center. If you can't find a flight that's convenient for your trip, you can also fly into Cascais (CAT), which is 11.4 mi (18.3 km) away.
Catch a ride on the metro at Quinta das Conchas Station for ease of access to the rest of the city.