United Airlines Cancels Flights, Warns Customers of Outage

United Airlines has issued a warning to customers and pre-emptively canceled several flights as the airline takes most of its systems offline for a controlled restart and cutover window for its SHARES reservation system.

As the airline braces for what it calls a "major system update" on Wednesday morning, United sent a message to its customers, warning them about what services will be impacted and for how long.

United Issues Statement to Travelers

Last week, United began warning its customers of the system outage, revealing that it had already canceled most flights that were slated to depart during the outage period.

"On February 4, 2026, from approximately 01:55-04:00 (Central time) United will be going through a major system update that will involve an outage of our Shares GDS. During this time, it will not be possible to see flight schedules, book travel, retrieve existing bookings, perform ticketing transactions, perform cancellation and/or refund transactions, or check in for flights using myIDTravel or ID90 Travel, as well as United’s own employeeRES or United app tools," United told its customers internally via a statement from The Points Guy.

United warned customers that most of its services will be unavailable during that time, warning them to "plan in advance."

"United has already pre-canceled most flights that depart during this time period. We strongly encourage staff travelers to plan in advance for this outage if they will need to travel on United, and book early. Additionally, we recommend checking in before the outage begins (check-in is open up to 24 hours before departure using the United app), especially if travel will commence shortly after the outage ends."

While this messaging from United indicates an outage of just over two hours, other communications show the window as 1:30 a.m. to 5:00 a.m., saying that it is a “technology upgrade which will restart our systems” to maintain “better functionality and reliability.”

What Will Be Impacted

During the planned outage, United.com and the mobile app, call centers, kiosks, travel agency channels and partner airline access will all be down.

As The Points Guy points out, this means several key features will be unavailable.

• Schedule display
• New bookings
• Reservation retrieval or servicing
• Ticketing
• Cancellations/refunds
• Check-in

Departures are also paused during the window, but already-airborne flights are expected to continue.