Short answer? Deregulation Act of 1978.
Real answer? Actually it is more of a case of retaining older aircraft to maintain competitive market share.
Until fuel prices went north of $100/barrel it was more economical to operate paid-for MD80's than purchase expensive 737-800's (FAA wire bundle debacles not-withstanding).
Now with fuel so dear, DC9 numbers in the US are dropping like a Beech Bonanza full of Doctors. At American we operate 325 MD80's with 45 slated for early retirement. Northwest has 92 even older DC9's that will see the scrap heap soon. United announced retirement of their entire 737-300/400 fleet last week (94 aircraft) and will consequently furlough 950 flight crew.
Myself, I am facing my second furlough from American in five years. When my former airline was "acquired", my seniority date was "adjusted" by 12 years and post 9/11 I went from a MD80 command position to the street in a year and one half.
Here we go again!!
Dave
