Transcript for Airports Still Recovering From Nationwide Customs Crash
to new reports after travelers were trapped from coast to coast. Computers went down last night causing long lines like these at Miami international. Missed flights as well, and the ripple effect lasted well into today. Passengers waiting for flights. ABC's gio Benitez now on what they say caused those computers to crash. Reporter: Airports and airlines still working to recover today from the nationwide crash of customs computers. Turn on the air conditioning! Reporter: In Miami, some 8,000 passengers stuck at customs through the night. Emergency personnel treating more than half-a-dozen people. There are thousands and thousands of people hot and sweaty, no water, there were people puking everywhere. Reporter: At that airport alone, 2,000 missed connections. During the four-hour outage on one of the busiest trachl Davel days of the year. In Atlanta, epic lines stretched through terminals. Scenes repeated at over 20 major airports. We were just trying to get home, it's been a long flight, six hour flight, and then stand in line for almost two hours. It's ridiculous. Reporter: Officials now telling ABC news the nightmare was caused by the failure of a software update, not a malicious attack. So many families trapped in line, and we saw people getting sick too, gio. A lot of people will be wondering, isn't there a backup system of some sort when these computers go down? Do they have to wait hours and hours and miss flights here? Reporter: Yeah, David. You know, there is a backup. It has access to the terror watch list, and it was used last night, but we're told it's very, very slow, and that raises concerns about how fragile this whole system can be.
This transcript has been automatically generated and may not be 100% accurate.