A TAP Air Portugal is in its last days offering trips between Lisbon or Porto and Ponta Delgada where children don't pay, having only the cost of airport taxes.
This promotion is valid for direct flights to Ponta Delgada and Terceira, from Porto and Lisbon and vice versa (except Porto-Terceira, which allows the connection via Lisbon). Each adult can travel with one child up to 23 months old and another from 24 months to 11 years old.
This offer is available from the 5th to the 18th of August, for trips to be made from the 01st of October to the 15th of November.
All information about the campaign can be found here: https://www.flytap.com/pt-pt/promo/criancas-viajam-gratis-acores.
TAP always offers free transport in the cabin of one personal item and hand luggage in all fares, including Discount.