Ryanair's UK-based pilots have said they will strike over two days later this month and three days in September.
It follows a ballot on industrial action that was passed by 80% of the 72% of relevant members of the British Airline Pilots Association (BALPA) who voted.
In a statement, BALPA said that following the result, its National Executive Council met and authorised the strike action by its members in the airline.
The first stoppage will begin at midnight on 22 August and last for two days.
The second will start at midnight on 2 September and run for three days.
The dispute centres on a claim by the pilots that is focused on pensions, loss of licence insurance, maternity benefits, allowances and pay structure.
"Decades of Ryanair refusing to deal with unions has resulted in two things," BALPA claimed in a statement.
"Firstly, a management that apparently doesn't understand how to work with unions, and secondly a company that doesn't have a number of standard agreements that any union would reasonably expect in any workplace."
The union claimed it had made no progress with Ryanair management on the issues and the airline had made no offer to its members.
Brian Strutton, BALPA General Secretary, said no pilot wants to spoil the public's travel plans "but at the moment it seems we have no choice".
However, the airline has said the strike has the support of less than 30% of Ryanair's UK pilots.
In a statement, Ryanair said that over 70% of their UK pilots are either not members of BALPA, did not vote in BALPA's ballot, or voted against industrial action.
Irish-based Ryanair pilots who are members of the Irish Airline Pilots' Association are also currently balloting on industrial action, with the process due to end on Friday.