Services from Inverness to Stornoway and Benbecula, and from Inverness to Kirkwall and Sumburgh, will be halted from Friday 17 March to Sunday 30 April.
In December, 73.5% of workers represented by the Unite union at 11 Scottish airports operated by Highlands and Islands Airport Limited (HIAL) voted in favour of outright strike action, and 92.8% in favour of action short of a strike.
The first walkouts were held last month, with Loganair warning ongoing "work-to-rule" industrial action was impacting its ability to operate its schedules confidently.
