Originally Posted by sailingfun

It depends on the airframe. 2.22 a gallon is still very high for fuel if you look at the last 20 years. Its pretty easy to do the math on what a aircraft that is 30 percent more efficient saves per month in gas. Its a big number and well beyond the cost to purchase or lease new aircraft. That is why most startups are now going with new equipment rather then old aircraft. This does not even take into account the maintenance savings. The MD-90 is a bit different because its fuel burn is the same as the newer aircraft making it a good deal at the moment.
This does not however change the fact that Delta had a aging fleet before the merger. Add in NWA's very old fleet and Delta faces serious capital costs to refleet the airline. Other airlines are doing it on a ongoing basis. Delta seems to be focusing on near term profits and not the long term outlook.