Do I not need to supply passport details when booking through websites?
I've booked international air tickets from a variety of sources and I've always needed to supply passport details, e.g. airline websites, travel agents. However I've just booked a flight with Expedia and at no point did they ask for my passport details.
Has anyone got some experience with this? Should I be concerned? Do I need to provide them at some point, or just when I show up at the airport to check in?
I have just had the same thing happen to me. What was the outcome? :)
Eventually I got access working to the airline's site and entered my details in there. I don't believe I _needed_ to, as I was never prompted for it, but I figured why potentially cause myself future hassle. My airline was Thai Airways BTW.
In some airline examples, it's only when you get to check in - either online or in person, that the passport details are requested. Before then you'd receive only a booking reference number, and you may be asked for your name and other identifying details (as you've stated Expedia did).
The booking number is enough to confirm it was your ticket, and at check-in, the passport details will be entered, either by you or the airline staff at the counter.
Does this vary by route or airline? I know some airlines seem very insistent on getting the details up front.
Often it's by destination country - some countries (notably the US) are very keen to hoover up all your personal details ASAP...