Millions of Americans across the U.S. are bracing for difficult weather conditions during the Christmas holidays as storms threaten to further disrupt one of the busiest travel times of the year.

Along the East Coast, the first storm of the winter blanketed cities from Boston to Baltimore with ice and snow.

Meanwhile, California residents are cleaning up the aftermath of a storm that brought gale-force winds, flooding and high surf on Monday and killed one man.

The weather events are further complicating travel plans for America, where air travel delays are already expected after American Airlines flights were halted due to a technology issue.

On the East Coast, winter precipitation is expected to impact many people’s travel, with areas like Boston and New York receiving heavy snowfall, while Baltimore and Washington DC are bracing for precipitation and ice.

On the West Coast on Monday, the storm caused a pier to collapse and three people to fall into the Pacific Ocean.

This storm’s waves reached 60 feet (18 m) and forced some evacuations. Flood and high surf warnings remain in effect on Tuesday.

Weather isn’t the only factor affecting holiday travel on Tuesday. Technical issues are also adding stress as millions of Americans rush to their travel destinations.

American Airlines flights were grounded early Tuesday after the Federal Aviation Administration (FAA) announced a “nationwide ground stop” due to an “issue with provider technology.”

The ground stop was lifted about an hour after it began and flights resumed, although not without a series of delays.

Delays were expected to continue on Tuesday, with some departures taking off two hours later than scheduled.

American Airlines apologized for the inconvenience and said, “It’s all hands on deck as our team works diligently to get customers where they need to go as quickly as possible.”

While many morning flights were delayed on Tuesday, most afternoon flights are scheduled to take off on time.