A computer systems outage affected multiple major airports including, SFO, JFK, O'hare in Chicago, Philadelphia international and others.
"It's the biggest line I've ever seen. It was really long. It went all the way pretty much to the plane," said Daniel Edwards.
RELATED: U.S. customs computer outage resolved, computers 'back up and running'
International travelers were welcomed to the U.S with the news: a system-wide computer outage.
The Gordon family had just landed from an 11-hour flight.
"(We waited) Maybe an hour and there were a bunch of flights getting off at the same time. It was down the hall, maybe up to the gates," said William Gordon.
Across the country, thousands of international travelers waited in long lines to be processed by U.S Customs and Border Protection. ✈️ @CBP is investigating system outage that affected major airports nationwide— Luz Peña (@LuzPenaABC7) August 17, 2019
Full story: ⬇️https://t.co/clOcPWCL1Q@abc7newsbayarea pic.twitter.com/vg01bd0VPb
The U.S Customs and Border Protection agency resorted to "alternative procedures."
In other words, they had no other option but to process these travelers manually.
According to SFO's on-duty manager:
-The system computer outage lasted 4+ hours
-Approximately 20 different airlines affected
-Approximately 30 flights landed during outage
-Arriving flight: Singapore, Paris, London, Amsterdam and others
While travelers waited inside to be processed, travel agents and family members also waited.
"The KLM comes from Amsterdam around 11 a.m. to 11:30 a.m. and we had to wait for them for almost five hours. They had been flying for 11 and a half hours and they just came out," said travel agent, Manuel Castillo.
Greg Bowman was waiting for his relatives coming from Germany.
"We just texted them just a few minutes ago and it has been two-and-a-half hours since they've gotten off their plane. So he told me it was going to be another half hour so we are looking at three hours," said Bowman.
CBP said it will continue investigating the outage and added, "There is no indication the disruption was malicious in nature at this time."