This holiday season had all the makings of a logistical nightmare. Thanksgiving fell late, shortening the number of days carriers would have to ship an unprecedented number of packages. The last time the season was so short, in 2013, United Parcel Service Inc. failed to deliver orders from Amazon.com Inc. and others by Christmas, forcing the sellers to dole out gift cards and refunds.
In the years since, UPS and rival FedEx Corp. have spent billions of dollars to upgrade their networks. This was a chance to prove it had paid off, but it was also a key test for the internal logistics arm that Amazon has been expanding with gusto since that fateful 2013 holiday season. In a Dec. 19 statement, Amazon said it was on pace to ferry 3.5 billion packages globally in 2019.