American Airlines has become one of the first airlines to guarantee that families can sit together on its flights.
The US flag carrier will face penalties if it fails to ensure that relatives get seats next to one another, having submitted its "family seating" plan to the US government this week.
In the plan there is a guarantee that children under 15 will be sat with their accompanying adult.
Passengers must be booked under the same reservation, and the airline says it can't uphold the promise if the aircraft is suddenly swapped for a smaller one.
"American Airlines lets families sit together at no additional cost," a spokesperson for the company told Insider.
"We are proud to offer industry-leading, customer-friendly policies that ensure a positive travel experience for families traveling together."
Until this point American Airlines has not charged families to sit together.
When booking a flight, they've been prompted to book their seats together at no extra cost.
The difference now is that the airline has legally formalised this process, and will "rebook you at no extra cost or provide you a refund if you choose not to travel" if it cannot provide the promised seats.
President Joe Biden praised American Airlines on Twitter and urged others to follow its lead.
He said "no one should have to pay extra to be seated with their kids" and that is it "time for more airlines to follow suit".
In the UK different airlines have different policies when it comes to seating families together.
For example easyJet's website states: "Whilst our seating system will always try to seat families together, seats are allocated on a first come first served basis so the earlier you check in the more likely you are to be seated together."
British Airways says that if you don't choose seats in advance it will "always do our best" to seat a family together, clarifying: "This may mean that you'll be seated in adjacent rows or across the aisle. All children under 12 will be seated with an accompanying adult. Anyone over 12 may be seated separately."
On Ryanair flights, it's mandatory for children under 12 (excluding infants) to be seated next to an adult they are travelling with.
The airline allows "a free allocated seat to a maximum of four children per one adult that purchases a seat".
Recently a mum told the Mirror how her son was left in floods of tears when a passenger refused to move out of his seat after Ryanair double booked it.
Ryan Bandli spent the flight back to the UK anxious and upset at not being able to sit by the window seat, which helps the six-year-old keep calm, with the airline blaming the issue on an IT glitch.
His mum Adi had forked out to reserve a specific spot on a plane run by the budget airline's subsidiary Buzz, only to find a woman sitting in it when they boarded the plane in Budapest, Hungary.
She showed them her identical seat reservation and refused to move, prompting the flight attendants to usher Ryan to an aisle seat.
Adi, who said her son is "very reactive" and struggles in stressful situations, said she the flight attendant had "begged them" to give their reserve seat up.
