Airlines don't handle the baggage, the airport handles the baggage.
There is no airport in the world I would trust to not break something breakable.
As a joke, I used to have stickers that said, "Fragile! Please throw underarm"
As a frequent traveller I used to consider the average life of a suitcase to be 3 flights. I've had them run over - tyre tracks right over their dented, mangled forms; crushed between baggage trucks; dropped from a height great enough to smash holes in carbon fibre [I buy expensive suitcases, airline services keep having to buy me new ones.]
Soft bags have a better survival rate, but provide zero protection for the contents.
So, short of a full-blown flight case[1], which will at least make the baggage handlers have to deal with it separately, you need to be able to get it into the cabin.
How you achieve that will depend a whole lot on the airline & whether you're flying in the good seats or down in the chickens.[2]
[1]which would cost more than the guitar. Cheap substitutes are not good enough.
[2]industry term for 'coach/economy'