For example, last year I was looking at Bogota, Colombia to LON. This was quite pricey, but it turned out if I bought separate tickets - Bogota to Orlando, Florida, and then an Air Berlin flight to London was pretty well priced.
Even better, I checked and it went via Dusseldorf. However if I just bought the leg to Dusseldorf, caught the 20 min train to Cologne and flew from there, it got cheaper still.
This of course requires hours of messing around with flight websites, and often knowledge (like that Dusseldorf and Cologne are close by). Surely there's a simpler way?
Eg, I'm looking at flights from Vancouver to Bangkok, and also from LON to either SCL or EZE or Lima or Quito. One to Quito goes to the Netherlands, somewhere in the Antilles islands, onwards to Guayaquil in Ecuador and then to Quito. 4 flights requires all sorts of playing to find the cheap legs, if any. Surely there's a 'cheapest paths' search engine that can take care of this somehow, or a simpler way?