Comment by lxgr

What Kiwi.com is doing with their "separate tickets plus connection insurance" model is called "virtual interlining", and it's an interesting alternative in some scenarios (well-connected airports with many alternatives). But I'd still never risk it on an important connection.

I've had a very bad experience with Kiwi.com myself: I booked a Ryanair flight on them without realizing that Ryanair is actively trying to prevent Kiwi from reselling their flights. Kiwi.com apparently works around this by booking tickets on pools of Ryanair retail accounts, to which they don't share the credentials with travelers – making mobile check-in impossible. (And Ryanair at least at the time was charging over 100€ of a "service fee" for a boarding pass print at the airport...)

This is only marginally related to booking separate tickets, but I suppose the larger point is that it's never a great situation to be stuck between the lines of two companies actively hostile towards each other, when you really depend on their cooperation to get to your destination.

"Official" interline agreements are an explicit statement that two or more airlines will make at least some reasonable effort to get you and your luggage to your destination, and will be on the hook for it (under ICAO regulations) if things don't work out.