Same reason AA went with both Boeing and Airbus. Using both means you can accelerate fleet renewal as each manufacturer only has so many delivery slots available.
I've always heard that when you have 100+ of a given type, there is enough economies of scale to justify the different types. I'm still a fan of one fleet type, but there are valid reasons to doing otherwise.
I've always heard that when you have 100+ of a given type, there is enough economies of scale to justify the different types. I'm still a fan of one fleet type, but there are valid reasons to doing otherwise.