I am using Air France/KLM when I travel to Japan since Air France started to operate flights between Paris CDG airport and Tokyo Haneda airport. Then, my member status rises each year. I reached Silver in 2017, then to Gold in 2018 and Platinum in 2019.
Air France has up to three daily flights between Paris and Tokyo. A daily flight to primary international airport, Narita airport and 1-2 daily flights to Haneda airport, which is closer to downtown Tokyo. KLM has 1-2 daily flights between Amsterdam Schipol airport and Narita airport. Both airlines use terminal 1 at Narita and also have daily flights to Osaka. If you have connection flights at CDG, it is quite easy. Flights to Japan depart and arrive at terminal 2E and if your flights are within Schengen area, flights depart from terminal 2F(except code share flights).
When you book flights, just watch out which website you are looking at. Air France website also offer KLM flights and KLM offers Air France flights too but the fares can be absolutely different. Even the fares can be different between Air France websites in Czech Republic and Japan. Also, please check carefully which airline operates your flights within Europe. It can be a code share flight, not operated by Air France or KLM. In this case, you might not get free drink and snack on board. If your connection time is quite tight, skip the code share flight and book the next flight operated by Air France/KLM.
Then, also sometimes Air France offers Premium Economy class cheaper than economy class. Air France's Premium Economy is quite nice and very worth to pay for it.
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