All United Airlines flights were grounded nationally this morning due to a "connectivity issue" before the ground stop was lifted 30 minutes later.

The Federal Aviation Administration issued the stop at the company's request across the U.S. and Canada between 1 a.m. ET and 2:30 a.m. ET — but it was then canceled at 1:30 a.m.

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The reason given by the Air Traffic Control System Command Center (ATCSCC) was simply "COMPANY REQUEST / TECHNOLOGY."

The airline told NBC News in an emailed comment: "United experienced a brief connectivity issue just before midnight Central time on Tuesday, but has since resumed normal operations."

FlightAware's " Misery Map " showing delays across the country showed 42 delays and 4 cancel

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