For what it's worth....
I fly alot with my bass(es). Like a TON. Mostly overseas to Europe and back to Canada but I've flown domestically in North America and in Europe as well with no issue. What everyone has to keep in mind with all of this is the "internet effect". In other words, if someone has something to complain about they are 100% for sure gonna let the world know on the webs. If everything goes ok..... (crickets)....
I use an SKB Bass Safe and check it. This is only because I have to fly with two basses and I can fit two basses in two separate gig bags inside that case. It's snug, but it's worked every time. I've lost count but I'd estimate I've checked my basses in that case in the neighbourhood of 50 times. All the guitar players in my band just bring one guitar each - because they are right handed and can rent good backups from our backline supplier - and they use gig bags and carry them on. We've had initial jive at the check in counter once or twice, but ultimately they always let them on the plane. The last couple of years it's been even better. KLM flight attendants see a guitar and will usually offer to put it in the first class closet.
So I guess what I'm saying is..... if you're gonna - or have to - check it, use a really good case. If you have a nice gig bag that ain't too bulky, just take it as carry on. (And maybe don't risk flying with an Alembic or Fodera or something.
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