United is upgrading its computers. Here's how that could impact travelers.

United Airlines is readying a large exertion update that volition instrumentality down its online preservation strategy aboriginal Wednesday.

The bearer is urging passengers with flights scheduled to depart connected Wednesday to cheque successful via United's website oregon mobile app connected Tuesday to debar encountering problems. United expects the outage to past astir 4 and a fractional hours, opening Wednesday astatine 2:30 a.m. EDT and lasting until 6 a.m. EDT.

An alert connected United's homepage informs travelers that it is "conducting a planned exertion upgrade" and that galore of its web and app services volition not beryllium disposable during that time, including for employees of the airline. 

United is modernizing its aging mainframe formation preservation system, known arsenic Shares. The upgrade requires the hose to transportation preservation information from its existent information halfway successful North Carolina to a much high-tech installation successful Chicago that the hose said volition amended reliability.

Here's what United customers should cognize astir United's preservation strategy upgrade. 

What if I americium flying connected Wednesday?

United's formation docket volition beryllium temporarily unavailable starting aboriginal Wednesday morning. Customers besides won't beryllium capable to marque caller reservations, cancel bookings, cheque successful for flights oregon retrieve their itineraries. 

As such, the hose is urging anyone scheduled to alert connected Wednesday greeting to cheque successful connected Tuesday. That is besides erstwhile passengers should cheque bags, which fliers tin typically bash up to 4 hours earlier departure.

The preservation strategy refresh has been planned for immoderate time, with United canceling impacted flights months ago. The hose notified customers of the changes, affecting astir 600 flights, astatine the time.  

Customers tin inactive book, implicit check-in oregon marque changes to their trips anterior to Feb. 4 astatine 2:30 a.m. EDT, oregon erstwhile the information transportation is completed. 

What could spell wrong?

United has rehearsed the information migration process, truthful things should spell smoothly, the hose told CBS News. Travel experts expect comparatively small disruption.

"Don't freak retired if you can't hunt for flights successful the mediate of the night," Scott Keyes, laminitis and CEO of formation deals website Going.com, told CBS News. "It volition travel backmost online soon.'

Of course, if the upgrade doesn't spell arsenic planned, it could spell headaches for customers. Roughly a decennary ago, Southwest Airlines suffered a machine outage that dragged connected for days, starring to hundreds of flight cancellations and thousands much delays.

Edited by Alain Sherter

Kris Van Cleave contributed to this report.

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