It is not possible to book flights with the airline
A Scottish airline said it had temporarily stopped taking bookings to protect customers while it sought to end uncertainty over its future.
Management at Highland Airways told employees at a staff meeting that the firm was not in immediate trouble.
However, the Inverness-based company was experiencing what they described as "continuing problems".
First Minister Alex Salmond said the Scottish government had a duty to protect lifeline services.
He said public agency Highlands and Islands Enterprise (HIE) was aware of negotiations to secure fresh investment for the airline.
Highland Airways links the islands of Colonsay, Coll and Tiree with Oban on the mainland and also Stornoway in the Western Isles and Inverness.
The airline also operates flights between Cardiff and Anglesey in Wales.
A management buy-out of the company in 2006 was backed by £620,000 from HIE.
The staff meeting was held at Inverness Airport.
A routine flight taking a delivery of newspapers from the mainland to Sumburgh in Shetland went ahead as planned.
Highland Airways was set up in 1991, as Air Alba, and has gone on to operate mainly island routes in Scotland and Wales.
It has also carried out other work including mail and fisheries protection duties.
In August, BBC Scotland reported that two fisheries protection aircraft operated by Highland Airways had been out of action for six weeks.
The Scottish government said delays in completing the necessary documentation had prevented the planes from flying.
The protection agency, established in 1991, enforces UK, European Union and international fisheries laws and regulations in the seas around Scotland and in Scottish ports.
It owns two Reims Cessna Caravan II F-406 aircraft contracted to Highland Airways and based at Inverness Airport.