Flag carrier Finnair is cancelling 128 of its flights on Thursday 19 June, due to effects of a ground staff walkout called by the IAU, the Finnish Aviation Union.
Thursday's four-hour industrial action will affect employees in ground handling operations and catering services, according to the airline.
Finnair cancelled more than 140 flights on Tuesday for the same reason.
Thursday's cancellations will affect the travel plans of more than 8,200 passengers. Finnair said it is offering affected customers alternative flights.
The walkouts stem from a dispute between the Service Sector Employers group Palta and the IAU, which has now continued into a sixth month.
The National Conciliator's Office previously announced the parties would meet for negotiations on Tuesday.
The National Conciliator's Office said that Tuesday's negotiations ended unsuccessfully, adding that talks between the IAU and Palta would continue next Monday.
"Customers whose flight was cancelled due to industrial action will be informed about the cancellation as soon as it has been done. After this, the customer will receive a message and be offered a new route," a Finnair press release read.
The airline noted that the cancellation has resulted in congestion of its customer service operations, prompting longer than usual wait times.
The aviation union has issued a new work stoppage warning for ground service staff on 2 July, according to the National Conciliator's Office.
It said the industrial action targets several companies in the aviation services sector and will affect air traffic.
Edited to reflect that the IAU has issued a new work stoppage warning scheduled on 2 July, and other new details.
