Expedia has grown far beyond a search engine for flights – it's now the parent company of a dozen travel brands including Trivago and Hotels.com – but according to VP of global product David Fleischman, machine learning has always been at the heart of the company's operations. The business of delivering quality flight search results is tough, and Fleischman describes it as an "unbounded computer science problem". The reason for this is because flight itineraries and schedules are constantly changing, and Expedia's proprietary 'best fare search' (BFS) has to 'learn' and adapt all the time. The extent of the problem can be summed up by one statistic. The average Expedia.com flight search will take three seconds to deliver results. In those three seconds you will see, on average, 16,000 flight options, in order of convenience or price or time. Get the full story at Computer World