Listed below are airlines flying to Portugal from the UK & Eire. (I’m intending to add information for other countries but haven’t had time yet).
For a link to the airline’s own website, click on the name. Also listed are where they fly to in Portugal.
UK & Eire:
British Airways – flights from Faro, Funchal, Lisbon and Porto to a wide number of airports in England, Eire, Northern Ireland, Scotland and Wales.
easyJet – flights to Lisbon from Bristol, Edinburgh, Liverpool, London (Gatwick or Luton); Faro from Belfast, Bristol, Glasgow, Liverpool, London (Gatwick, Luton, Southend or Stansted); or Porto from London Gatwick; or Funchal (Madeira) to London (Gatwick or Stansted).
Ryanair – flights to Porto from London Stansted & Liverpool or flights to Faro from Birmingham, Bournemouth, Bristol, Doncaster, East Midlands, Edinburgh, Glasgow Prestwick, Leeds Bradford, Liverpool, London Stansted & Liverpool.
TAP Portugal – flights between Lisbon, Porto and Funchal (Madeira) with Aberdeen, Belfast, Dublin, Edinburgh, Glasgow, London (Gatwick or Heathrow) & Manchester.