That morning I went by bicycle from my house to Sapporo Station. I did not have to pay extra for the bigger luggage in the train. I just made sure that I enter the last car of the train. Then my next worry was at the airport, but the lady at the check-in counter just asked me if this is a 'normal' bicycle or a racing bike and if it is possible to take it on the conveyer belt for luggages. I choose to define my Araya bike to be the latter and said it should be handled with care. So she handed the bag to another attendant and I saw him disappear through a door with my bike. The strange feeling that I would see my bike again did not disappear.
When I was waiting to board the plane I saw that my bag was loaded with great care onto a conveyer belt and into the plane. So it was not put into a container for transport! Great, I thought.
Then in Sendai my normal luggage came out of the plane in the normal procedure, but here again, the bicycle was brought by an attendant. As adviced by the person who sold me the bag I immediately opened it and checked the bike for damage, but there were none. Once you leave the baggage claim area, then claims (sorry for the pun) about damage are not valid anymore.
The same procedure took place when I went back to Sapporo, so I have to say that I am very positively surprized how careful bicycles are handeld on DOMESTIC flights. I ahve heard other stories for international flights, but I haven't tried that yet.