It is up to UA not QF as it is within MCT; QF to QF would be no problem to change, esp. with QFF status equivalent to DM I've flown over million miles with DL and now avoid them like the plague due to various problems, so not sure using DL as the target responsive airline is the best choice Bottom line is cross-alliance connections generally mean no favours but only contractually required service, so going QF/UA is the problem and UA controls what happens. As for tight connections, I've made QF to UA within 30 min of landing, so it is possible but requires the stars to align (and have made QF to AA within 20 min but with concierge help). LAX isn't soooo bad of an airport if you know your way around.