I have a suspicion that travel agents deliberately alter their sites from time-to-time, to make life hard for screen-scrapers. It's within their perogative: why should they make life easier for "bottom-feeders" who want to make money off their hard work? I would not encourage any attempt to make money that way.
You mentioned skyscanner.net, and their reliability: are they screen-scraping? I don't see any IATA IDs on their site, and they call themselves a "search engine", not a travel agent, so that's what I suspect they're doing. It is often possible to reverse-engineer the queries websites use, if you examine the web pages and see what they're doing, even if it's in JavaScript.
I see that Skyscanner is offering an
API, which you might like to play with for learning purposes. Their method requires the webpage to load a single JavaScript, which provides functions that you then call (in the page) to get data or a map back i.e. it responds to manual queries. if I had a need to try this, I would want to code some PHP or Python on the server, and try to examine their Javascript to see what they're actually doing - the POST or GET queries.
One last little thing: web pages returned by a server are often divided internally in to DIV sections, so it's possible to isolate a relevant portion of a larger page by splitting off that DIV. Again, that's a programming thing e.g. some would use JavaScript on the client browser, while I would prefer PHP or Python on the server.