UPS plans to deliver about 36 million packages Tuesday, its busiest day of the year, up from 35 million last year. That includes all the shipments at Worldport, a massive sorting facility located between the Louisville airport's two main runways, plus those traveling by truck. If you're still shopping, Amazon Prime might be your answer: Shoppers have until 9 p.m. PT Tuesday to click the order button and still have presents arrive by Christmas Eve.