50c next airport from this one, page-47

Macdonnel Douglas moved into Military applications as did all the others as R&D is easier to obtain.

The reason they and i mean all airlines hedge their bets on both manufacturer is due to bargaining power with both the airframe manufacturer and the engine combinations, thats 1.

Another is finacing arrangements and availabilty.

Also when a service bulletin or airworthiness directive is issued the have alternate types and models that may escape the rigour of the inspection.

Parts is also an issue.

There are more, but to criticise QANTAS for Beoing aircraft purchase or visa versa is short sighted as each company will have a composite mix in its fleet at different times.

All the best.