Q. We bought a ticket from Lufthansa, but with flights on both Lufthansa and United to Europe recently. On the outbound flight, there was a mechanical problem which caused us a two-day delay. Although there were seats on other airlines (we checked) that would have gotten us to our destination as planned, Lufthansa/United said that since we were on a "non-published" discount fare, they could not put us on those other airlines. In the past when there's been a problem like this, the airline in question did indeed put us on a competitor's flight. What is a non-published fare, how do you know when you've booked one, and do all airlines have this sort of "you buy it, you fly it" policy?
A: Looks like you bought a "consolidator" fare. And yes, the way you were handled was typical in the airline industry. Non-published or consolidator fares are fares that are considerably lower than the fares you might find on the airline's web site or on Kayak, etc. You can identify them either by asking whatever source sold it to you, or by simply noting that it's way lower than what you can find by other means. Sites like Lessno.com and some travel agencies and cruise lines deal in this type of fare (they're also sometimes called "bulk" fares). And yes, most airlines adhere to this policy.
One thing to note however: had the problem happened on your way back from Europe, since it was clearly a mechanical problem (within the airline's control), you would have been protected by fairly stringent European Community laws specifying levels of compensation. In this instance, you would have been entitled to up to 600 Euros (about $900), but again, only if the problem arose when leaving Europe, not flying to.