The company said “the volume of air packages in our system exceeded the capacity of our network immediately preceding Christmas so some shipments were delayed.” Some of those shipments were from online retailers, like Amazon, which was reportedly coming off its biggest year yet. Amazon had promised customers that packages would arrive before Christmas. A spokesperson for UPS seemed so embarrassed by the debacle, she couldn’t do anything more than repeat the fact that UPS and Amazon have an agreement. “We have a relationship with Amazon.