The Doona in my opinion is one of the best purchases I made for travelling. A pram and car seat all in one, so easy to use, Very light weight and their are lots of accessories if required. I used this for 7 Trips away, 5 of which were abroad and one by train (it even fits in the Isles to push, and small enough to go on the seat). Not only is it great for travelling but extremely handy when nipping out and about or in a different car than your own. We got 10 months use before my daughter grew out of it, the same as a baby car seat.
Now for the first few months we used a baby sling, these are great, and they roll up small to fit into their little bag so handy for travelling. However they do get a bit hot when in warm countries. I’ve since discovered a pack away carrier, light weight, safe and waterproof, as seen on my blogs its travelled some miles with us.