Should I pay for an extra seat for my infant?

If the child is under 2, you don't have to, but it's safer to have them in a car seat for the duration of the flight. If you can afford it, buy the seat.

How do I ensure we sit together?

Pay for seat selection during checkout. Do not rely on 'gate assignments,' as families are often separated on full flights.

Booking Transatlantic Flights for Families

To secure the best experience, prioritize overnight flights to sync with sleep schedules and book directly through the airline's website. Always choose a 'multi-city' search if visiting two distinct regions to avoid backtracking with tired children.

Use Incognito Mode and Tools. Search for flights using Google Flights in an incognito window. Use the 'Track Prices' toggle 3–6 months in advance to receive alerts for your specific route and dates.
Select the Right Routing. If flying with kids under 5, choose a direct flight even if it costs 15% more. If you must have a layover, ensure it is at least 3 hours to account for slow walking speeds and security lines.
Verify Seat Configuration. Before paying, check the seat map on SeatGuru. Avoid seats near bathrooms to minimize noise, and confirm you aren't in a row where the armrests don't lift, which makes sleeping impossible for toddlers.
Book via Airline Direct. Avoid third-party aggregators. If a flight is delayed or cancelled, customer service will only help you if you booked directly through the airline's own portal.

Should I pay for an extra seat for my infant?: If the child is under 2, you don't have to, but it's safer to have them in a car seat for the duration of the flight. If you can afford it, buy the seat.
How do I ensure we sit together?: Pay for seat selection during checkout. Do not rely on 'gate assignments,' as families are often separated on full flights.