Ryanair passengers travelling with a young child will have to pay extra for a reserved seat, the airline has announced.
Under the low-cost carrier's existing rules all passengers can choose to save money by having their seats randomly allocated.
But the Dublin-based airline said this has led to "boarding issues" as crews try to re-seat adults and children who have been separated.
From September 1 adults travelling with children under 12-years-old will have to purchase a reserved seat.
A standard reserved seat costs £8 per flight, according to Ryanair's website.
Children under 12 will receive a reserved seat free of charge.
Ryanair's chief marketing officer Kenny Jacobs said: "Ryanair is Europe's number one airline for families and this summer all customers are enjoying fares that are 10% lower than last year.
"That's a four euro (£3.37) saving on every flight and these changes will allow parents to save another four euros for every one of their children travelling together.
"It will also allow families to select their preferred seats at the time of booking, check-in for their flights up to 30 days prior to departure and fly safe in the knowledge that they are getting Europe's lowest air fares, while ensuring that they always sit with their children.
"This will also prevent other customers who have chosen to purchase a seat of their own from being displaced on board."