American Airlines has issued a travel alert on Tuesday to give passengers flexibility who were impacted by a technical issue on Christmas Eve. The airline said a “vendor technology issue” caused a temporary grounding of the airline’s flights on Tuesday morning during the busy holiday travel season.

American Airlines said on Tuesday its flights had resumed after a technical glitch forced the carrier to issue an hour-long ground stop, disrupting travel for thousands on Christmas Eve, one of the busiest periods of the year.