The Greek island of Kefalonia is to be served for the first time by British Airways from Heathrow.
Summer-only flights will run twice a week on Tuesdays and Saturdays between May 15 and October 6.
Return fares start at £118 and £398 for business class.
The number of flights to European destinations such as Ibiza, Santorini and Split are also being increased .
BA chairman and chief executive Alex Cruz said: “We’re always developing our leisure offering from Heathrow so are incredibly pleased to be adding Kefalonia to our network.
“The launch of our new summer routes, which also include Figari in Corsica and Almeria, mean we will be flying 39 more routes in 2018 than we did in 2016 – an increase of 17%.
“Next summer, Ibiza will go from four per week to a daily service, Mykonos will be served six times a week from four, while an additional weekly flight will be added on to the airline’s schedules to Olbia and Split.