Six airports across Scotland will be closed to flights over three days as air traffic controllers strike 24-hour walk-outs in a dispute over pay.

Prospect union members are resuming industrial action, having rejected a revised pay deal from Highlands and Islands Airports Limited (Hial).

Inverness Airport will be shut to air traffic on Sunday, and Sumburgh and Kirkwall Airports on Monday as union members stage 24-hour strikes.

On Tuesday, Stornoway, Benbecula and Dundee Airports will be closed.

Hial said the offer rejected by air traffic controllers comprised a retention allowance which would have seen them benefit from an additional £10,000 over a five-year period.

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Managing director Inglis Lyon said: "We deeply regret the inconvenience and upset to hundreds of passengers affected by the strike action.

"We wish to find a resolution to this dispute as soon as possible and would urge Prospect to sit down with us once again to find some common ground on which we can arrive at a negotiated settlement.

"Our position has been consistent throughout. We can only deliver an affordable settlement within the terms of Public Sector Pay Policy.

"So far, Prospect has continued to ask for a pay increase far in excess of what we are able to afford and that unfortunately remains the situation.

"We remain committed to resolving the dispute. Our latest offer of a retention allowance of £10,000 over a five-year period remains on the table and will continue to explore potential solutions within our affordability.

"The continued industrial action is having a significant impact on our passengers, communities and the airlines operating from our airports.

"We would encourage Prospect to revisit the offer and bring this dispute to an end."

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Air traffic controllers previously went on strike on May 23, when the six airports were shut for 24 hours due to the industrial action.

Prospect national secretary Richard Hardy said: "Hial and Scottish Ministers have left our members with no option but to strike.

"We have been seeking to resolve this dispute for more than a year and this action is only being taken as a last resort.

"Strike action is by its nature disruptive but if we are to safeguard the long-term future of air services in the Highlands and Islands we have to start paying air traffic controllers a fair wage.

"This is the only route our members see available to them to achieve this."

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Hial is a public corporation wholly owned by the Scottish Ministers.

A Scottish Government spokesman said: "We continue to encourage both Prospect and Hial to work towards a resolution to the pay dispute, which is clearly not in the interest of passengers or the communities served by Hial airports.

"Hial has been authorised to develop a retention allowance as part of the Air Traffic Management 2030 Strategy programme. We have been clear with both Hial and Prospect that any settlement must be in line with Scottish Public Sector Pay Policy.

"Hial has implemented a pay rise for all staff, which is a significant improvement on previous years, as well as significantly increasing their contribution to their pension scheme in order to maintain this benefit for employees.

"In the face of the UK Government's continued budget cuts, the Scottish Government has delivered a distinctive and progressive pay policy for 2018/19 - one which is fair, supports those on lower incomes, and protects public sector jobs and services while delivering value for money for the people of Scotland."