DL's web site cannot search by price on multi-city itineraries. I know this is a longstanding bug that has been reported before. But what I didn't realize is that it also prevents DL results from being returned on third-party sites like Kayak when searching multi-city itineraries.

I was searching a multi-city itinerary on Kayak and found it odd that there were no DL results returned at all and no option in the navigation pane to choose DL flights. Then I realized what the problem might be, and went to DL.com to search directly. I got the standard error, then tried searching by schedule, and DL actually came out with a lower price than any of the results on Kayak.

If I hadn't remembered the DL.dumb bug at that moment, I would have booked on a different airline. DL must be losing business because of this glitch.