In an ideal world, they'd pay.
However, having flown for three different airlines and worked for three (big) companies in a previous career - including recruitment and management - none of them remimbursed expenses. The same goes for the dozens of other interviews I've attended over the years. The only exceptions were two sandpit based airlines that paid for a return ticket for the interview, plus a night in a hotel. And they only did that because otherwise no-one would make a 6,000 mile return trip for an assessment. The last company - in fact the only one - that offered to pay my travelling expenses to an interview was way back in 1990. God I feel old.
It's not just airlines, it's the modern world I'm afraid. Airlines - make that employers in general - don't expect to pay expenses and candidates generally don't expect to claim them. It would soon change if everyone refused to attend interviews unless their expenses were paid, but I suspect that's as likely as no-one paying for a type rating . . .