Jet Fuel and Cargo Companies
If you look at the large cargo companies (FedEx, UPS, and DHL), they all have "antiquated" aircraft. Some of them include DC-8, DC-9, DC-10, and the 727. Major airlines replaced these jets 5,10,15 years ago for many reasons, but I have to believe that the economics of operating these aircraft were a big reason why they were replaced. Since these cargo companies are making money right now, it seems logical that now would be a good time to invest and replace these aircraft with ones that are cheaper to operate, and have a more useful cargo load.
What do you think about this? Why haven't these been replaced even as jet fuel skyrockets? Should they or shouldn't they be replaced?
Thanks for your opinions.