Since I hear so much about the advantage of Cross-Crew Qualification for Airbus aircraft, I have a little something to think about. In fact this problem is taking place in real life at at least one airline, probably more.
Say you have a captain flying your DC10's and a brand captain flying your MD-80's. Now you're renewing your fleet with A320's and A340's. One becomes captain of the A340 and earns $7000 a month and the other one becomes captain A320 earning $5000 a month. Of course you train both captains to fly both the A320 and the A340.
One day they call the A320 captain to fly from A to B - a 6000 nm trip -. Now this captain who earns $5000 dollars a month is flying 270 passengers for about 16 hours. Another day they call up the A340 captain to fly the A320 for a 1500 nm trip. Now a $7000 dollar a month captain is flying 140 passengers for about 3 hours and back.
How is the A320 captain gonna feel about that. And more importantly: HOW IS THE UNION GONNA FEEL ABOUT THAT !!
To tell you the truth very, very few airlines are buying airbus because of this feature and those who have, have found out the troubles behind it.
Let me know what you think.