Strike action has been threatened over plans to centralise some air traffic control at Highlands and Islands Airports Limited (Hial).
Hial has proposed controlling air traffic at five airports from a central hub in Inverness.
The Prospect union said some members were unwilling to relocate, meaning nearly 50 could lose their jobs.
Prospect said it had balloted its air traffic control members on industrial action.
Hial said its plans did not involve compulsory redundancies. Managing director Inglis Lyon said a date had been agreed with Prospect for discussions on resolving the row.
Under Hial's plan, unmanned towers would be located at Sumburgh in Shetland, Dundee, Kirkwall in Orkney, and Stornoway in the Western Isles.
They would feed information to the central hub in Inverness.
Prospect has claimed the plans would also lead to the downgrading of air traffic control at Benbecula and Wick airports.
The industrial action, if approved by members, would take the form of action short of a strike starting on 4 January next year, with individual one-day strikes taking place after that date.
Prospect said its members believed Hial's plans would cost jobs and have a "devastating effect" on island communities by "reducing safety and damaging the economy".
Hial said its air traffic management system needed to be transformed to meet operational needs now and into the future.
It said digital tower technology had been operational since 2015 and was already being used, or in the process of being introduced, for Norwegian, Swedish, German, Dutch, Danish, Belgian, Irish and UK air traffic management.
Mr Lyon said: "The threat of industrial action is likely to create uncertainty and frustration for communities, our colleagues and airline customers and that is an outcome we hope all parties will seek to avoid."