The US Customs and Border Protection computer system is back to normal after it was down at some airports, creating long lines for arriving international travelers Friday afternoon.
O'Hare and Midway International airports tweeted as of 6 p.m., processing of international arrivals is back to normal.
US Customs and Borders tweeted about the computer glitch after 4 p.m.
"CBP is experiencing a temporary outage with its processing systems at various (airports) of entry & is taking immediate action to address the technology disruption," US Customs and Border Protection tweeted. "CBP officers continue to process international travelers using alternative procedures until systems are back online."
"CBP officers are working to process travelers as quickly as possible while maintaining the highest levels of security," it said in a second tweet.
Authorities do not think there was anything nefarious about the outage, a Customs official told CNN.
John F. Kennedy International Airport in New York tweeted that passengers were being processed manually.
A tweet from a woman at JFK showed a long line of passengers.
"People are growing frustrated. Nothing like landing after a 10 hour flight to this," Sarah Baird wrote.
The outage appears to have occurred around 2:30 p.m.
Micah Lillard, a spokesman for the Metropolitan Washington Airports Authority, said airport operations are running as normal.
A tweet from Los Angeles International Airport said, "... please check with your airline for the latest status of any flight impacts."