Ronnie Chua/Shutterstock.comFor the second time in three months, United Airlines’ flights have been hit by a computer glitch.

　　The carrier tweeted on Sunday at about 8 p.m. ET that an “IT issue” had forced it to ground all domestic flights.

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　　A ground stop is in place for domestic flights due to an IT issue. We’re working on a resolution. We apologize for the inconvenience.

　　— United (@united) January 23, 2017

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　　However, a follow-up message posted an hour later announced it’d lifted the ground stop and was “working to get flights on their way.”

　　UPDATE: The ground stop has been lifted. We’re working to get flights on their way. We apologize for the inconvenience to our customers.

　　— United (@united) January 23, 2017

　　It’s not clear when United took the decision to halt its domestic services, though a message tweeted at around 7 p.m. by a passenger on a delayed United plane indicated the problem lasted at least a couple of hours.

　　#unitedairlines have you tried unplugging the system, and plugging it back in? I’d like to go home now. UA224 EWR – MSY pic.twitter.com/bDHiBxNOge

　　— Matt Edens (@mgedens) January 23, 2017

　　The airline is yet to elaborate on what caused the glitch.

　　The incident will come as an embarrassment to United as it’s the second time for it to happen in three months. In October, a number of its flights were delayed for several hours when a computer issue affected its weight reporting system.

　　And no, such troublesome technical issues aren’t the preserve of United. In the summer of 2016, Delta was forced to cancel flights following a global computer system outage at its hub in Atlanta, Georgia, while American had to delay a number of flights in 2015 when some pilots’ iPads – used to store important flight documents – started malfunctioning.

　　We’ve reached out to United Airlines for more information on this current issue and will update when we hear back.