If UPS could do it, it would. The 727 is a popular training aircraft. Passenger 727 were widely flown until the mid-2000s, and the plane is still popular among freight carriers. Meanwhile, UPS is paying storage fees on aircraft it retired during the downturn -- DC-8 and classic 747. Passenger DC-8 flights pretty much ended in the 1980s (and nearly all remaining freighters were retired with fuel stored) -- because of this, it's seen as an old aircraft and nobody wants them. And the 747 is just too huge to be a training aircraft most places.