After seeing overwhelming shipment volumes far above expectations on Cyber Monday, transportation and logistics major United Parcel Service (UPS) said this Tuesday that the “bubble” at certain package centers has worked its way through the system for the most part.

UPS does not expect any delays over Christmas because of this surge in volume but, between Nov. 27 and Dec. 2 its Express unit’s on-time delivery rate came in at just under 90%.

In contrast, rival FedEx boasted 99% on-time delivery rates during the period in question, says ShipMatrix, Inc.

But UPS is expected to deliver almost 750 million packages over the peak season, while FedEx estimates are about half that – about 400 million.

United Parcel Service Inc. (UPS) drivers deliver packages on Cyber Monday in New York, U.S., on Monday, Nov. 30, 2015. Online sales on Cyber Monday may rise at least 18 percent from a year earlier, slower growth than during the holiday weekend, as consumers start their Internet shopping earlier, according to forecasts by International Business Machines Corp. Photographer: John Taggart/BloombergA

The Cyber Monday surge also required UPS to implement a 70-hour work schedule for drivers over an eight-day period. However, UPS reportedly did not first consult with local unions.

International Brotherhood of Teamsters General President James Hoffa sent a letter to UPS CEO David Abney saying that this was the third consecutive year in which Cyber Monday orders have overwhelmed the network’s delivery capacity.

For the first time, UPS this year has implemented a 27-cent surcharge for packages sent to U.S. home addresses during specific weeks of the holiday season.