Due to the length of Duty PHX needs flight crew bunks. BA management when they bought the first batch of 777s decided it would only do E coast and Mid East and never do long range so wouldnt need bunks, so they expensively got Boeing to take the standard fit bunks out (for a CSDs office, much more important). The Rolls Royce engined aircraft had them fitted but theres only 16 actually 15 of which only 10 have first class. 3 are on the SYD run on any one day so theres not much flex. 6 744s a week provides the same capacity ish as 7 777s.