I'm in need to carry my Kronos 61 to a intercontinental flight, but I'm not sure if I should buy a hardcase and give it to baggage (which doesn't feel very good ), or is there any softcase that I can use in a similar situation of bringing an electric guitar onboard?
Bring a softcase and bluff your way through it. My friend has always done this. They don't like it but it never failed. The one time he gave it to baggage it was in a full flight case and still arrived broken in two. Say you called beforehand, that the band can't play without you're an artist, whatever.
I would never give my keyboard to baggage handling.
I've done a few flights with my Kronos 61 in SKB's ATA case. I didn't use the silly plastic corner pieces that it came with, but instead packed the borders firm with 1-inch charcoal foam. I also did dozens of flights with my Triton Extreme 61 in a 76 key case the same way for years before. Never once had a problem.