[rob74]

Not sure about Boeing and McDonnell Douglas, but for the many European aircraft companies that first cooperated under the Airbus name and then (much later) merged into a single company, there wasn't really an alternative (unless you consider bankruptcy an alternative). Even in the late 1960s, when the original A300 was designed, that task was more expensive than any individual European manufacturer could shoulder, and without a new product, they would have quickly faded into irrelevance.

https://en.wikipedia.org/wiki/History_of_Airbus#1970%E2%80%9...