United Airlines cleared a massive four-and-a-half-hour shutdown of its entire operation on Wednesday as it embarked on one of the biggest ever tech upgrades in its history, taking critical services offline and grounding planes as the Chicago-based carrier tries to rid itself of rapidly aging legacy computer systems.
Flight booking, check-in, and MileagePlus accounts were all inaccessible during the upgrade on United’s website, and passengers couldn’t just call the airline’s customer support line instead… that had also gone dark during the planned outage.
In a message posted on United’s website, the airline explained: “We’re currently conducting a planned technology upgrade from 1:30 – 5:00 AM CST, and many of our services will NOT be available for anyone during that time, including United employees.”
Planes that were due to depart before the tech upgrade were allowed to take off as normal, but some flights had to be retimed, and others were cancelled.
No doubt the airline’s executives were watching nervously on at United’s corporate headquarters at Willis Tower in downtown Chicago, and keeping their fingers crossed that the tech upgrade went to plan.
Like many airlines that have been around for so long (it is celebrating its centennial year in 2026, after all), United has long relied on decades-old legacy computer systems.
Some of these mainframes date back to the 1960s and were originally coded by tech giants like IBM. Over the years, airlines have stacked newer computer systems on top of these aging foundations, but the cracks have been growing bigger for years.
According to chief executive Scott Kirby, the airline has spent “hundreds of millions” to create its own cloud-based computer systems, but you don’t just move an entire airline’s IT infrastructure into a new environment overnight.
In fact, United has been moving systems from its old mainframe to the cloud bit by bit over the last few years. One of the last moves, and perhaps one of the most important, is happening tonight.
Kirby says United is unique amongst legacy US carriers in so aggressively replacing aging IT systems, because it’s a hard process with no immediate return on investment. A tough call to make when you work in a low-margin industry.
While airlines are getting better at adding tech upgrades to improve the customer experience, the backend is often still working on legacy systems that have been responsible for devastating operational meltdowns in the last few years.
From a passenger’s perspective, Wednesday’s early morning shutdown won’t bring any immediate overnight improvements. This upgrade is all about making United’s IT infrastructure fit for the future, improving the airline’s resilience, and making way for tech improvements in the years ahead.
Thankfully, a spokesperson for United told us that the upgrade went according to plan, and that operations actually resumed earlier than originally expected.
Everything was smooth as silk for my 6a flight out of ORD this morning…seems like all went as planned
Kudos to United.