Originally Posted by
fredandgingermad
Unfortunately the only car seats available in the UK for use on a plane are forward facing only, (Britax Eclipse and a couple in the Kiddy range) the bulk of car seats in the UK are designed for use with a 3 point seat belt only
The Diono Radian 5 rear-and forward-faces and works on a plane:
https://uk.diono.com/product/radian-5/
Dionos are great seats. They are extremely heavy, but they do fold and have backpack straps for transport. This seat would last a long time for your child -- and it would allow him to rear-face for a long time, too.