We never had to ask - all of them offered straight away after or during an initial telephone interview. If they want to see what your hubby can do then surely it's up to them to sort out his airfare etc?? Maybe they're just hoping you're going out there anyway for a trip but hopefully once they realise you don't have one planned they'll stump up for the ticket etc.

If it were me, I'd just ask them as if I expected it so they would hopefully realise it's the norm i.e. 'will you send my ticket or shall I book it and then you can reimburse me?'.

Go get 'em!! Good luck.