It’s starting to sound like all too familiar a refrain. Due to an IT error, a major airline has to temporarily issue a full ground stop on all its flights nationwide, causing a cascade of problems. Today’s “winner” of systems glitch roulette is Delta, and travelers this morning may have cancellations and delays to look forward to.

The problem began around 6:30 p.m. ET on Sunday. At 9:15 p.m., Delta confirmed that a “systems outage” had resulted in departure delays and cancellations for flights still on the ground. Flights already in the air were not affected, but did experience delays when landing at some airports.

At 10:15 p.m., Delta updated its news site to mention that oh, by the way, delays aren’t accurately showing on information screens, the website, the Delta app, or, in fact, for reservations agents — so not only might your flight be delayed or cancelled, but also you can’t actually find that out in advance.

Delta later confirmed that it had cancelled 170 flights on Sunday — and that no, those delays and cancellations were still not necessarily being reflected in any avenue through which customers can actually receive information.

Delta resolved the mystery outage sometime after midnight, the airline reports, and the “vast majority” of its Monday flights will take place as scheduled. However, 110 flights have already been cancelled, and more cancellations are possible.

The airline is waiving the change fee for affected customers who need to rebook flights scheduled for Jan. 29 or 30, for travel completed by Feb. 3.

Delta CEO Ed Bastian issued an apology to customers, saying, “This type of disruption is not acceptable to the Delta family who prides itself on reliability and customer service. I also want to thank our employees who are working tirelessly to accommodate our customers.”

Luckily for Delta, Sunday night is a comparatively slow travel time and so the impact of this outage is minor in comparison to others. Delta had a more severe systems outage last August that grounded all go the airline’s flights worldwide on a busy Monday morning for several hours.

But glitches or outages in core IT systems look like an increasingly pressing problem in air travel: just since July, Southwest, British Airways, and United — twice — have experienced similar problems, causing rippling issues for hours or days.

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