Since the start of February, Ryanair has been allocating seats at random unless passengers pay an extra charge of up to £10 to choose to sit together - even if they have booked together.
Fiona Buchanan, from Newbuildings, was making arrangements to travel from Derry to London to visit a sick family member and assumed that the rule would not apply to young children.
But, while her one-year-old daughter was required to sit on her lap as is common practice for infants, her four-year-old was separated from them.
According to the boarding passes, little Mollie would have to sit in Row 8 and her mum would be back in Row 24.
Having not realised until the boarding cards were printed and she was unable to go back and pay the extra charges, Fiona is now worried about her daughter being left with strangers during their flight.
She is left asking how she is supposed to supervise the little girl, and what would happen in the event of an emergency.
When I went and spoke to Ryanair, they said: 'You should have paid the premium.'
When contacted by UTV, Ryanair pointed to the FAQs on their website and quoted one of the points.
"We will endeavour to seat families together, however this will not always be possible. If you want to be guaranteed seats together we recommend that seats are purchased," it says.
"If you chose not to select and purchase a seat and have been randomly allocated seats which are not together, please contact our call centre so that we may try to assist you."
UTV further questioned how separating a four-year-old from her mother complies with the airline's own policy of not carrying unaccompanied minors under the age of 16.
But the subsequent response simply reiterated that position.
Fiona has been advised that "cabin crew discretion" may be used to make changes to the seating plan after boarding - but, while she is hopeful that will happen, there is no guarantee.
On the return flight, which it transpires was not full at the time of booking, she and Mollie have been seated in the same row but not beside each other.
"Why should I have to have the privilege of sitting next to my daughter? There is a duty of care surely," Fiona said, speaking about their outbound flight.
"Adults, yes, not a problem - by all means, pay the fee.
"If she was in the same row or in the row in front, maybe I could cope with it for the short flight that we're on. But she's 16 rows away at the front and I'm at the back."
Ryanair does not carry unaccompanied minors under 16 years.
Fiona feels she, and other parents are being pressured into paying the extra charges - which apply to each individual seat. For a family of four, for example, to book seats together, the extra charge could be up to £40.
"I've already paid £150 for the flight, so what is that actually going towards?" Fiona added.
When the situation was discussed on U105's Frank Mitchell Show, some callers said they would pay the charge for the sake of sitting beside their child.
But many others felt that there should not be any question of young children being separated from their family, raising issues including health and safety and child protection.
One caller also added that it was unfair on other adult passengers - some of whom may actually have paid the charge to choose their own seat beside travel companions - to effectively force them to take a degree of responsibility for someone else's child.
Fiona says the episode has put her off flying with Ryanair, but had she not been caught off-guard by the extra charge and already printed the tickets, she would have reluctantly paid it on this occasion.