Air Southwest will cease operations from airports in Devon and Cornwall months ahead of its original plans.
The regional carrier will stop flights from Plymouth from September 14 and from Newquay on September 30.
Air Southwest had originally planned to maintain flights until Plymouth city airport is closed in December.
The airline, which runs a fleet of four Dash 8 aircraft and employs almost 150 staff, said it was originally planning to operate while Plymouth airport remained open.
In a statement Air Southwest said: “Despite our original hopes, forward bookings are significantly lower than required and the level of demand is not financially viable.
“The Newquay flights have been reviewed at length, but are not viable on their own without the association with Plymouth. As a consequence, Newquay routes to Glasgow, Guernsey, Jersey and Manchester will also end on the same date.
“Newquay services to Aberdeen, Bristol, Cork, Dublin and Leeds/Bradford will end on September 30, which regrettably will be the last day of Air Southwest branded flights.”
Passengers booked to fly after these dates will be fully refunded, the airline said.
Loss-making Plymouth airport, owned by Sutton Harbour Group, is to shut in December. Air Southwest, established in 2003, was sold by Sutton Harbour to Humberside-based Eastern Airways last September.