Anxiety can be an absolute bastard with ASD. Those suggesting a 9 yr old child should just suck it up and learn that it's just the way of the world have absolutely no fucking idea how bad things can get.
I've had my autistic child sobbing down the phone and desperate for me to come home (wildly different circumstances but still separation anxiety/needed the reassurance of me being there).
Sleeping in a blow-up bed isn't the issue although the change of sleeping arrangements may be tough. But expecting a 9yr old ASD child not to be able to stick to their normal sleeping time/routine and instead to wait up until everyone else has gone to bed will absolutely cause chaos and significant distress.
Obvs the relationship between OP and her ex has broken down - she says the ex won't even let DS speak to her on his birthday. I don't think it's a huge leap to suggest that the ex isn't properly considering DS's needs and instead is intent on punishing OP. I wonder how much he genuinely wants the contact or whether it's about depriving OP of it. Pure speculation obvs, but just based on the snippets of information here, he doesn't seem to especially put his child's needs first.
I probably would have gone and got DS now, but that's me. I understand why OP didn't and probably in the long term it's better that she didn't. I am pretty sure that DS won't tell someone at the airport to call his mum, even if he's upset. Just the idea of DS being in a different country though - Jesus, that's hard. If he has a total meltdown there's no way to reach him, you'll just have to wait it out til he's back. Listening to an autistic meltdown is horrible, it's so distressing - and depending on the child, it can go on for hours.
By the way, the PP who called it a "tantrum" at the airport can fuck right off. Go and educate yourself about autism.
OP, hopefully things are calmer in the morning. Once DS is en route he might feel OK. Sometimes the lead up to events and all the changes are the hardest but when he's there, the excitement and fun might take over.
But absolutely agree with @PyongyangKipperbang - keep everything as evidence and go and get legal advice. I think the visitation rights need to be looked at again. A diagnosis of ASD makes everything very different and if your ex can't or won't consider his additional needs, then the same contact may not be appropriate.
Hope you're OK.