Ryanair is being investigated by the UK's competition watchdog over charges it imposes on parents to sit next to their child on flights.
The Competition and Markets Authority (CMA) said it was looking into whether the fees, which the watchdog said typically costs £8 each way, were "unfair" under consumer law.
It said Ryanair's terms and conditions state a parent must sit with their child if aged between two years and 11, and this is done through what the airline calls a "mandatory family seat" that the parent must pay a fee for.
Ryanair called the investigation "bogus" and insisted its family seating policy "fully complies with all relevant laws".
The CMA is looking at whether the airline's "approach to seat reservations may mean parents are being charged for the airline to meet its child safety and disability‑related obligations as set out under aviation rules rules – and will investigate to determine whether or not this practice is in line with consumer law".
The watchdog said it understood that Ryanair was the only major airline flying out of the UK to impose such a charge.
It said other airlines offered to seat children next to a parent or guardian without a fee, or allocate seats together automatically during booking for free.
Ryanair said adults travelling with children pay one reserved seat fee, "but can select reserved seats beside them for up to four children on the same booking FREE OF CHARGE".
"This means that parents travelling with children pay for only one (adult) reserved seat but pay nothing for the four other reserved seats for their children travelling with them," it added.
"Ryanair looks forward to disproving these false CMA claims during this bogus investigation."
