The A321's are 12 years old. The 4 eldest A320's are 9/10 years old and the rest are from 2004 on. So maintenance costs are much higher and tech delays far more common.
The A321 burns about 15% more fuel than the A320 so if the A320 is full, you need 200 on the A321 to start justifying the extra fuel burn alone. It's a common day to fill 174 seats but a whole lot rarer to fill 200 plus, and that's in the summer. In the winter, it just doesn't happen.
If it's more profitable to fly 174 pax in a 320 than 199 in a 321, then bye bye 321. Simple as that.
You make some very interesting points - but I wonder is the situation as clear cut as that? From personal experience, I have been on several 100% full EI A321 flights this year and in the past, I've never experienced them being anything but at least relatively full.
It may be more profitable on specific routes to fly 174 pax in an A320, but there are other considerations to be made - Ancillary Revenue, etc - all incremental to the main fare.
For EI to dispose of all of the A321s and not to replace them with identical units or similar capacity variants, they would have to be certain that on a year round basis that the lost revenue, contribution, ancillary revenue and passenger number potential from consolidating to an explicitly A320 short haul fleet would be outweighed by consistent profitability generated from operating only the A320.
The A321 has proven to be very useful in cases of Irr-Ops, for example during the Volcanic Ash crisis etc. There is a demand for it on certain routes on the EI network - for example Malaga during the summer (even with an A330 operating the morning flight) along with AMS, BRU etc.
If the units are being replaced like for like, for example when the four A320s arrive during 2011, then EI will be left reduced capacity potential on several routes - unless they add frequencies which would be erroneous and highly unlikely considering the net capacity difference would not warrant this. This may also not be possible if fleet utilisation is already near the maximum.
EI Premier