As many 5,000 passengers have had summer travel plans disrupted by strikes at six Scottish airports.
Air traffic controllers employed by Highlands and Islands Airports Limited (Hial) have taken the action in a dispute over pay.
The first of three 24-hour strikes was held at Inverness airport on Sunday.
Sumburgh and Kirkwall airports were shut on Monday and Dundee, Stornoway and Benbecula airports on Tuesday.
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The walkouts caused more than 100 flights to be cancelled, including 74 operated by Loganair.
The controllers’ union Prospect said the strikes were “a last resort”.
Hial managing director Inglis Lyon has apologised for the disruption to passengers.
He said: “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.
“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.”
But Lyon added: “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 remains on the table and we will continue to explore potential solutions within our affordability.”
The Scottish government, which owns Hial, has urged the company and Prospect to hold fresh talks to resolve the dispute, the BBC reported.
More: Series of strikes to shut Scottish airports [July 9]
