It is a second conditional - if and past + would.
It is expressing the unlikely/impossible… if my wife had a holiday (but she doesn’t) she would be flying to Madrid tomorrow.
Zero conditional - regular or general truth - if my wife has a holiday she goes to Madrid.
first conditional - possible - if my wife has a holiday (it’s possible, but not certain), she will fly to Madrid tomorrrow.
second conditional -
third conditional - in the past - if my wife had had a holiday, she would have flown to Madrid yesterday.
that’s just a very basic outline, but i hope it helps.