Aircadet - unfortunately, certainly after September 11, we are in a situation where there are more airliners in a servicible condition than are needed by the world's airlines. So airlines really have little choice but to store. Sometimes they are stored awaiting a new buyer or lessor, sometimes they are stored with the intention of bringing them back into service as the market picks up.
Certainly large ammounts of stored aircraft are not a great thing for established airlines - it results in the resale value falling significantly on your fleet, which is not a good thing. On the other hand, it provides an opportunity for new airlines to pick up newish aircraft at low prices.
Perhaps the most pressing issue with a large fleet of young airliners in storage is that it makes it hard to sell new aircraft. This means production lines become unviable, and have to be shut, perhaps earlier than would be ideal (e.g. 757).
Whatever way you look at it, storing aircrsft does present a number of problems to the market as a whole. However, it is part of the reality that the industry has to live with and deal with...
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