Comment by lxgr

I'd be very careful with Kiwi. They don't have official OTA agreements with all the airlines they resell; at least Ryanair at one point was actively hostile towards them, and Kiwi was working with personal Ryanair accounts to get around their roadblocks. This in turn meant I couldn't access Ryanair's mobile boarding passes and had to find a printer on short notice at the airport.

While airlines can apparently not legally completely prevent such "uncooperative" third-party resellers, and I do have some sympathy for the business model, it's not great to be stuck between travel agent and airline when things go wrong.

Other OTAs like Experian actually take the role of a good old travel agent (the entity historically doing much of the ticketing work the airlines are now doing directly) and will usually only sell you itineraries of interlining (i.e. cooperating) airlines, and also only of airlines that accept travel agents as business partners in the first place.