Although in the midst of “the busiest days in the history of the company,” according to a Fedex spokesperson, the world’s two biggest carriers say they are managing to stay ahead of the onslaught of holiday packages.  UPS has set estimates at 30 million packages a day for this week, almost twice the volume it handles on a typical day. Fedex says it is experiencing volume about 10 percent higher than during peak holiday times last year.