Interesting (to me anyway). In my experience most "in-country" Asian air travel is on Airbus, but, not yet having made reservations for the in-country segments, I just checked and was rather surprised to find that almost all JAL in-country segments are on Boeing 737-800 aircraft (
not the same as the ill-reputed 737-MAX8 and 737-MAX9 disaster craft). For a few segments JAL does fly the dreaded
737-MAX8.Even without the Boeing consideration I've been waffling about whether or not to rely exclusively on rail travel in-country. With last Fall's 70% fare increase in the JR RailPass, the cost is about the same for rail and air (a 14-day pass is about $800 even before the "supplements"). Air is faster, but not that much faster for short hops. For example, I can walk 100-200 meters to the Tokyo monorail or Shinjuku station and be on a train and on the way long before getting to either of Tokyo's airports and high-scrutiny security. Rail is more scenic. Air reservations can be made easily and many months in advance. Air also accrues frequent flyer benefits. The JR RailPass can be used on many city subways and skytrains, but not on the non-JR trains. The JR RailPass online purchase from outside Japan is somewhat convoluted and reservations can only be made 3 months in advance.
It's a bit whacky. You could buy a voucher for a JR RailPass today, but it wouldn't be delivered by Global Mail until a month before your designated validity date. Meanwhile you'd be making reservations 3 months before your intended travel. Then, you can only pickup your pass and actual tickets (Don't lose 'em!) in Japan at designated JR offices (e.g., in Haneda Airport near the Tokyo Monorail entrance). Also, if you want to use the fastest shinkansen trains, you have to separately purchase "supplemental" tickets.
There are many good things to be said about Japan, but their intricate rules and processes are not among those good things. When I was in school there many years ago I was advised to avoid speaking perfect Japanese because the moment that you do, you are expected to know and adhere to all the rules (even gift giving) and are no longer due the indulgence and forgiveness that gai-jin otherwise enjoy.
Just for laughs, here are the Tokyo, Sapporo, and Kyoto transportation maps. To figure out from the maps whether or not your train is JR or private is a real "Find Waldo" task. Part of the adventure! "Take half as much clothing and twice as much money," was my Grandmother's advice and rule for travel. I still miss her.