Loyal Airlines - Airlines that side with a manufacturer in this case.
Hmm. I don't really see the point of being loyal. Except that sometimes an airline can be able to reap small discounts.
I think some loyal airlines include:
Some not loyal airlines are
Singapore Airlines - (eg, MD-11 - A340, A340 - 777, 747X - A380)
QF - (their recent Airbus order)
CI - (their recent Airbus order)
I think airlines are in it only for their gain. The manufacturers I think, can only compete it they build aircraf that are better than the other manufacturer.
That's my €10000 and two cents!