Flights at seven Scottish airports including Inverness and Dundee will be grounded next month because of an air traffic controllers strike over pay.
The 24-hour shutdown on 26 April will also affect Benbecula, Kirkwall, Stornoway, Sumburgh and Wick.
But Highlands and Islands Airports Limited (Hial) warned passengers of potential disruption from Monday when a work to rule by air traffic control officers is due to start.
A total of 133 flights will be cancelled due to the strike.
A Hial spokesman said: "To allow our passengers to plan, we are progressing on the assumption the strike action will go ahead and the airports will close to air traffic for the 24 hour period on 26 April.
"Air traffic control officers are undertaking industrial action to support their claim for a double-digit wage increase in 2018/19 or a long-term commitment to above inflation pay awards.
"The evidence provided in the analysis of air traffic controller pay at non-Hial airports that [union] Prospect jointly undertook with Hial did not support a double digit wage award.
"Hial have scheduled a meeting with Prospect and the Advisory, Conciliation and Arbitration Service (ACAS) on 9 April, 2019 in a bid to reach a mutually agreeable solution to resolve the ATCO pay dispute.
"As this date falls after 1 April, the work to rule due to start on that day will come into effect.
"We anticipate there will be some disruption as a result of the work to rule and apologise in advance for the inconvenience this may cause.
"We continue to work closely with our airlines to minimise potential disruption wherever possible.
Hial said passengers should check its website for information during the action period at https://www.hial.co.uk/hial-group/air-traffic-control-dispute/
Highlands and Islands Green MSP John Finnie said: “Scottish Ministers own Hial and have an obligation to staff and communities to ensure a fair settlement is agreed.
"So far, ministers have been reluctant to get involved, despite it becoming increasingly clear that those running Hial on behalf of the Scottish Government aren’t delivering for remote, rural and island communities.
"It’s time ministers rolled up their sleeves and sorted this mess out.”
Prospect negotiations officer David Avery said: “Members demands are reasonable and they need to be addressed.
“They are not seeking parity with Heathrow or Gatwick, but other smaller airports.
“They have received a decade of below inflation pay rises while the rest of the industry, in response to a global shortage of controllers, has moved ahead.
“The company already struggles to recruit controllers and this is having an impact on services at some airports.
“By asking for support from ACAS we hope to find a way forward in these talks.
“However, ministers’ instructions to HIAL severely limit the companies negotiating position, so we also need to see these revoked.”
A Scottish Government spokesman said: “It is disappointing to see the union announcing industrial action, which will clearly impact passengers.
"We encourage both parties to continue dialogue in an effort to reach an agreement.
“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.
"Staff also continue to receive generous annual leave, sick pay and other allowances.
“In the face of the UK Government’s continued budget cuts, the Scottish Government 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.”