Incoming mail will now be delivered by boat as the mail plane becomes export only.
The move by Royal Mail is designed to reduce carbon emissions and brings post deliveries in Guernsey into line with Jersey and the Isle of Man.
Guernsey Post say they will deliver the post it as soon as it arrives, but tell householders and businesses to expect a '24 hour transit delay.'
The mail plane will continue to operate into Guernsey, but will fly in empty.
It will leave each evening principally with outgoing mail.
A spokesperson for Guernsey Post says it is hoped to use the inbound 'dead leg' in the future.
West Atlantic will continue to operate the service until the end of May and then new operator ASL Airlines will take over.
The French company operates scheduled, charter and cargo flights and is based at Charles de Gaulle airport in Paris.

Guernsey charity sees more 'in work' families requesting help
Guernsey deputy backs pavement speed limit
Survey reveals islanders’ concerns over misogyny and body image
Plan to reduce violence against women and girls in Guernsey and Alderney
Guernsey Airport scaffolding expected to stay for 'a couple more years'
Calls to reduce pavement surfing in Guernsey
Alderney vicar delivers life saving CPR
App launching to tackle loneliness in Guernsey