A surge in online shopping this holiday season left stores breaking promises to deliver packages by Christmas, suggesting that retailers and shipping companies still haven’t fully figured out consumers’ buying patterns in the Internet era. Companies from Amazon to Kohl’s and Wal-Mart having promised to deliver items before Dec. 25, missed some delivery target dates. United Parcel Service Inc. UPS -0.06% determined late Tuesday that it wouldn’t deliver some goods in time for Christmas, as a spike in last-minute shopping overwhelmed its system. “The volume of air packages in the UPS system did exceed capacity as demand was much greater than our forecast,” a UPS spokeswoman said. Consumers were reporting missing deliveries from FedEx as well, although a FedEx spokesman said the company wasn’t experiencing significant delays.