a few thoughts, take them as you will:
1) Expedia (or any other airline travel booking site) probably isn't the example when discussing 'above/below the fold' considering all the relevant info (ie searching dates/times/flights) is almost ALWAYS presented in the immediate hero section.
2) people know to scroll down... It's 2017, and is quite ubiquitous in practice. Not to take away from your point on this, as presenting the most important info as the first thing visitors will see is VERY important... and also a no brainer. However, making a statement such as,
"... the rest of the content that lives on these landing pages is pushed below the fold and likely never discovered at all."
is somewhat of a fallacy that often leads to misguided (and overgeneralized) assumptions. There are dozens (way too many tbh) articles— both in favor and in defense— regarding the entire "above/below the fold" debate. Case in point: