Ken:
It doesn't always fit down the aisle of the plane (esp in economy).
With that in mind, here are two caveats to my original note --
1) Reassure the airline staff that it is in fact a car seat (they will be eager to "check" it for you as you board)
2) My husband usually places our daughter in it, collapes the wheels, and then carries it (with her in it) in his arms as we are boarding & exiting the plane.
I used to do the same when travelling solo with our daughter, but now that I'm pregnant, that's not an option. Suggest to your wife that she ask one of the male attendants or a kind fellow traveller to help her board/exit when she is solo -- though she might be able to manage alone!
I always carry a baby sling with me, so that I can "wear" my daughter on my hip & carry the Sit 'N Stroll off the plane, if need be.
3) The seat WILL fit into an economy seat on KLM. Make sure you are not booked in bulkhead (where the arm rests don't lift up). Simply lift the arm rest in the seat, and wedge the Sit 'n Stroll in. It should be a perfect, tight fit.
You will find that the product is brilliant for tooling around the airport, as well as a secure, comfy seat for your daughter to rest in once you are actually on the plane.
Again, it is not a flawless product, but it beats any other options I've seen -- especially on the very long haul flights.
Best of luck & safe travels!
[This message has been edited by Caligirl (edited 06-03-2007).]