An S&S coupled frame and case makes it much better but not always easy. The airline part is simple as a piece of normal luggage. Lugging a 50 lb. case without wheels around a big airport or on the street is no fun but a lot easier than with a large cardboard box and no handles or straps, Disposition of the case while riding is a matter of planning and negotiating on the ground. I've had hotels hold the case until the return from a loop tour. I've also had UPS/Fedex sent the case forward to be claimed a week or two later. That may be more complicated across international boarders.
In Spain and France just before COVID I found regional trains to be very good with free bike sections on each train. Those networks cover large areas with frequent schedules. The intercity and high speed trains do not accommodate bikes like this, if at all. In Central America "chicken buses" gladly carry your bike along with all kinds of cargo on roof racks. A dollar to the conductor hauling it up the ladder makes for a very happy lad. To bad it's not a common practice around the world. In El Salvador I had to pay $2 for the extra seat my S&S case took up.
Where there's a will there's a way.