British Airways is to start a five-times a week service to Haneda, Japan, on February 19.
The airline said it wanted to open up the domestic Japanese market to UK travellers.
The outbound leg from Heathrow is scheduled to depart at 8.00am and arrive at 5.00am the following day.
The return journey leaves Haneda - which is 19 kms from the business district in Tokyo - at 6.25am and arrives in London at 10.00am the same day.
After March 26 both services will depart one hour later.
The service will operate on Monday, Thursday, Friday, Saturday and Sunday.
BA said it intended to continue its five times a week service to Narita airport - 66 kms from the business district.
The Haneda route will be serviced by a Boeing 777, with a four-class configuration - First, Club World, World Traveller Plus and World Traveller cabins.
Ticket prices start from £721, said BA.
British Airways also revealed that it will start a daily direct service to Buenos Aires on March 27. The flight to the Argentine capital currently stops in Sao Paulo, Brasil.
On the leisure side, BA is increasing the number of weekly flights from Gatwick to Barbados from 10 to 12, to Antigua from five to six, while the shuttle service between St Lucia and Port of Spain will also increase from five to six services.
Services to Cancun will increase from two to three flights per week from next summer.