PHILADELPHIA (CBS) -- An issue with the system that creates flight plans is causing a "small number of delays" for United Airlines.

According to CBS News' Kris Van Cleave, the airline began experiencing delays with the system sometime before 6 a.m. ET.

It is an outside system known as Sabre that several airlines use to support their reservation and operations systems.

United told CBS News that it is a network-wide issue with that one system, and not a system outage.

Airline spokesperson Erin Benson said it is causing a "small number of delays," but there have been "no cancellations."

The airline is currently working on the issue.