Ryanair has announced that they will be cutting the Dublin-based fleet from 30 to 24 planes for the winter 2018, which is said to put 300 jobs at risk.
The six planes will be transferred to the carrier’s Polish charter airline, which it said was growing rapidly.
Ryanair blamed their downturn in forward bookings and airfares in the Republic of Ireland, partly as a result of recent rolling strikes by Irish pilots.
Atleast 100 pilots and 200 cabin crew have been given 90 days’ notice.
The airline said their services “may not be required from 28 October onwards”.
It added that it would be offering transfers to Poland and possibly other bases, in order to minimise redundancies.
Ryanair said its profits in the April-to-June quarter had been hit by higher wage costs as the airline faces strikes by staff over pay and conditions.
It said higher oil prices and a fall in fares also dented profits, which fell 20% to €319m (£285m).
Ryanair is said to be facing more strikes. Cabin staff in Spain, Portugal, Belgium and Italy are walking out, forcing the cancellation of 600 flights.
The airline’s chief operating officer, Peter Bellew, said its board had decided to allocate more aircraft to markets where it had a stronger growth.