And you thought your holiday hangover was rough.

Monday night, a computer shutdown of U.S. Customs and Border Protection systems at airports across the country led to major headaches for travelers nationwide.

People returning home from the New Year's holiday weekend were being processed at international terminals by hand at several airports, resulting in long lines and short tempers.

"U.S. Customs and Border Protection is experiencing a temporary outage with its processing systems at various air ports of entry and taking immediate action to address the technology disruption," the agency said in a statement Monday night. "CBP officers continue to process international travelers using alternative procedures until systems are back online. Travelers at some ports of entry are experiencing longer than usual wait times and CBP officers are working to process travelers as quickly as possible while maintaining the highest levels of security."

About 10 p.m. Monday night, Miami International Airport said its system was back online but said it would take time for passengers to be processed.

Earlier, the airport said the outage was nationwide and said officials were working to restore the system.

Travelers took to social media to vent, beg for help and share photos of massive lines and wall-to-wall weary passengers.