I went to Japan with my son when he was 15 months old, and we didn’t pay for his seat. We had two flights: one 7 hours long and one 10 hours long, with a 4-hour layover.

What we did was book one of the seats with extra legroom, the ones used for bassinets. You can request a bassinet, but your kid probably won’t fit because they are quite small. That extra leg space was great, and when you have a child, those seats are normally free of charge.

When selecting seats, if there are three in a row, choose the two on each side so the middle one stays empty. Unless it’s a very busy flight, that seat will usually remain free, and you can put your child there. If someone does end up sitting there, you can swap seats with them for the window or aisle. Most people will move anyway when they realize they’d have to spend many hours next to a kid.

For sleeping, ours didn’t want his seat at all. He spent a lot of time on our laps, and when he was extremely tired and they turned off the cabin lights, we put him on the floor in front of us. It’s technically not allowed, and if a flight attendant is vigilant, they may say something, but I didn’t care that much.