The air traffic control pay dispute is being stepped up with rolling strikes to hit different airports on different days.
Earlier this week Prospect tabled a counter-proposal to Highlands and Islands Airports Ltd.
This was rejected by the company following a meeting on Thursday.
David Avery, Prospect negotiations officer said: “While we will seek to avoid disrupting major events as much possible, any strike action is disruptive by its nature, particularly during the school holidays.
“We would like to reiterate that we have been seeking to resolve this dispute for more than a year and this action is only being taken as a last resort.”
Prospect is announcing the following 24-hour strikes.
- Inverness - 21 July.
- Sumburgh, Kirkwall and Wick 22 July
- Dundee, Stornoway and Benbecula 23 July
The work-to-rule previously announced will continue.
The strike means flights from Stornoway will be disrupted or cancelled on both Sunday July 21st and Tuesday July 23rd. This will affect the Hebridean Celtic Festival weekend.
In addition, problems with holiday cover and aircraft delays could mean flights being cancelled across the network at short notice on any day.
Not all the HIAL airports are affected. Barra, Campbeltown, Islay and Tiree are unaffected.
Following the rejection of HIAL’s latest offer by union members on 28 June, HIAL met with Prospect on Thursday 4 July.
The offer rejected by Air Traffic Controllers (ATCOs) comprised a retention allowance that would have seen ATCOs benefit from an additional £10,000 over a five-year period.
At the meeting Prospect presented a pay claim that once again significantly exceeds the flexibility and affordability of a publicly-owned organisation.
Inglis Lyon, HIAL’s Managing Director said: “We are dismayed that Prospect has announced further days of strike action and apologise sincerely to our customers, passengers and local communities for the continued disruption.
“It is disheartening to have received a counter offer from Prospect that is beyond our affordability.
“Over the past eight months we have discussed various options with the Union and have been clear throughout that any proposal must be affordable and within the terms of Public Sector Pay Policy.
"Prospect are aware of HIAL’s budgetary restrictions and our latest offer constituted compromise to accommodate trade union demands within the bounds of the pay policy.
“We remain committed to resolving the dispute and our latest offer of a retention allowance of £10,000 over a five year period remains on the table.
“The continued industrial action is having a significant impact on our communities and the airlines operating from our airports.
"We would encourage Prospect to revisit the offer and bring this dispute to an end.”