Technology

I don't know, this sounds a lot like DNA evidence. Sounds great in theory, but doesn't actually mean what TV implies it to mean. In terms of a receipt, you still need to tie that to a person, or the wallet to the person. Given how easily people have lost their wallets, it'll be a similar issue to "My credit card was used at that time". Yes, the wallet / CC was used at a place at a time, but who was the person using it? In either case, they'll want to use the security video or clerk witness testimony to tie it together.

I'm not even sure what situation you're thinking that the airline would not accept their own printed ticket or shot of the ticket PDF or whatever they send you today, but the NFT would make all the difference. Again, either the Airline system reads your ticket data, whether it's NFT, barcode, or traditional digital and can tie it to a sale in their system or they can't. They can lose the NFT link just as well as the barcode link, and the gate agent isn't going to understand or care that you have an NFT that cryptographically proves "blah blah blah". They're already checking ID. For someone to fake the barcode version, they would also need a fake ID or Passport to match it.

I sort of see what you're saying if you went to court, and the airline wouldn't do discovery or purposefully shredded their records of your ticket for some reason, but we already have receipts and bank statements and the like that do the same thing, and an NFT doesn't change needing to prove you bought it in this case, presumably via linking a wallet rather than a bank account, though wallets don't have the ID requirements bank accounts do, so in court that could actually be rather harder to do.