United Airlines had no choice but to cancel its domestic operations Sunday after it suffered from a computer problem. Passengers all over the country were forced to wait for more than two hours. United spokeswoman Maddie King said that a ground stop has been issued due to an IT issue and domestic flights have resumed. However, passengers could still experience delays despite the announcement.

Sources said that a ground stop had to be enforced and United is working to get passengers going, said CNN. King apologized to customers and explained that they had to halt all mainline flights. "We are working as quickly as possible to resolve this issue and get our customers to their final destination."

Ground stops were issued for United's mainline flights or flights that are covered by its main operating arm, not its subsidiaries. This is given when there is a problem with the communications system of aircrafts that are used to send info to operations. Important pieces of information include departure times and weight and balance which are important in determining takeoff speeds.

Planes that were already in the skies are not affected; only those that are yet to depart. There were no details as to how many passengers were affected or how many flights were cancelled during the two-hour wait, according to ABC. Ground stops are simply in place to be "incredibly cautious."

The announcement that mainline flights were resumed and the ground stop has been lifted were given three hours ago but after an hour, another announcement was made at United Airline's official Twitter page saying "UPDATE: Additional delays are expected as we work to get flights out this evening. A travel waiver is in place."

This is not the first time that a technical glitch stopped United flights. In October, flights were delayed because of a computer problem and it lasted for hours. The airline said that it had problems with its weight reporting system and that it took time to get resolved.

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