Calculating Which is the World's Longest Domestic Flight

What is the longest plane flight you can take without leaving a country? The answer could be pretty simple and make for a very short video- but first we have to define what we're talking about. Does a "domestic flight" mean a regularly-scheduled airline route? Does it mean that you don't have to have a passport or move through immigration? Does it mean within a nation proper, or do overseas territories count? And are we talking about a currently-existing route, or one from the past? That's what makes this video from Half as Interesting, well, interesting. He goes through several flights that might be contenders for one reason or another, and eliminates them due to any of the reasons above. Yes, we have a winner, but you'll still learn about geography and aviation history along the way. This video is less than six minutes long; the rest is an ad.