<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by Empress:
Then I wonder how come AC doesn't just reconfigure their aircraft before each flight. So if the flight is overbooked and J is wide open, they can just take some J seats out and put more Y seats in.
I know... stupid idea. 
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I believe Lufthansa has their inter-European fleet set up so that they can adjust C and Y seating capacity to meet the demands of the particular route the aircraft is flying. I'm not sure how often the seats are adjusted on each aircraft.