We have many threads on this topics. The aim of this one is to collect resources for readers and make it a "Top Question" for an easy access. I am starting this with the EU and the USA. Please add any other you might know. Thanks.
In the European Union, there is one set of rules that is applicable to all airlines flying to/from the EU. Details on
They also made an app available on several OS: …europa.eu/transport/…mobile.html
In the USA, the D.O.T. rules apply to all US airlines. They can be found here:
The FAQs are easier to read. And on the left side menu, the "Travel Tips & Publications" section is also worth a visit.