Virgin Atlantic is to stop flying to Saint Lucia from next June after 21 years.
The airline said it was not “a decision that had been taken lightly”.
Virgin ran a three-times-a-week service to the island from Gatwick. Flights will continue to operate until June 8 2020.
Flights to Grenada and Tobago will now connect through Antigua.
Virgin’s Gatwick-Antigua service will increase from three times a week to four from June 8 2020 and its Havana service will move from Gatwick to Heathrow.
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The Havana service will be served by an A330-300, increasing Upper Class capacity by 63%.
The airline said it intends to increase flights from Gatwick to New York JFK and Boston with full schedules announced at a later date.
Virgin said it would continue to serve hotels in Saint Lucia through connecting flights via its partner airlines.
A statement from the company said: “As part of a recent network review, we’ve evolved our Caribbean offering, to ensure we continue to serve destinations most loved by our customers.
“It’s never easy to withdraw from a destination and it’s not a decision we’ve taken lightly.
“We’d like to thank our customers and teams in St Lucia for their loyalty and dedication over the last 21 years and are sad to say goodbye to this fantastic island.”
The Saint Lucia Tourism Authority said it “could not meet the proposals from Virgin Atlantic” which led to the decision to withdraw its UK service.
A statement from the tourist board added: “We want to thank Virgin Atlantic and Virgin Holidays for their commitment and support over the past 21 years.
“Our arrivals figures are growing steadily and this year we are on track to beat our record year in 2018. We look forward to continue working with our trade partners now and in the future to welcome more visitors from around the world to Saint Lucia.
“There is still significant air access with nine direct flights per week from the UK to Saint Lucia, with a daily flight from British Airways, and weekly from Tui and Thomas Cook.”