Operations were back to normal at Miami International Airport Friday following a five-hour computer breakdown the night before that disrupted critical databases at MIA and other international airports and caused extraordinary passport control delays.
The MIA outage delayed immigration processing of more than 2,000 arriving international passengers.
Russ Knocke, a Department of Homeland Security spokesman in Washington, told The Herald that agency technology managers believe the problem was caused by a computer virus.
But Knocke said experts had not determined the origin or nature of the virus.
On Wednesday, a computer "worm" invaded various computer networks in the United States, Europe and Asia, including media, business and government outlets. CNN said a small number of computers in an administrative office at San Francisco International Airport had failed Wednesday because of the worm.
Thursday's 6-to-11 p.m. failure added to ongoing delay woes at the Miami airport, recently classified as having the country's slowest immigration lines.
A congressional report in July said that on average, MIA immigration inspectors took about 50 minutes to process a planeload of international travelers, compared to an average of 30 to 40 minutes at other airports around the country.
U.S. Customs and Border Protection, which oversees passport control, has blamed the processing delays on outdated facilities and uneven distribution of flight arrivals at MIA concourses.
The Miami-Dade Aviation Department, which manages MIA, has pinned the blame on understaffing of immigration booths, a charge Customs and Border Protection denies.
Two other factors contributed to making the computer disruption here more significant than at other airports: It came at peak arrival times -- between noon and 7 p.m. -- and MIA is the busiest airport in the country in terms of foreign visitors.
In fiscal year 2004, MIA handled more than 3.8 million foreign visitors -- ahead of New York, Los Angeles, Honolulu, Newark and San Francisco.
Zachary Mann, Customs and Border Protection spokesman in Miami, noted that non-computer delays had eased in recent days. The agency's figures show that during the Aug. 8-14 period, MIA passport control wait times reached or exceeded 50 minutes only once -- on Aug. 13.
Mann said Thursday's computer problem was unusual for its duration.
Previous computer glitches have been relatively short. Mann said a regional computer problem two weeks ago lasted about two hours.
In 2002, immigration service officials acknowledged that a database used by inspectors to check whether travelers are terrorists or criminals suffered periodic, but short-lived, outages.The database contained lookout bulletins from several law enforcement agencies.
Mann said the database disrupted Thursday is used to process foreign arrivals -- but he would not provide details.
At first, Mann said, Customs and Border Protection computer managers expected the system to be up and running again in 20 minutes. But it didn't happen.
Passport control supervisors switched to a backup plan under which terror and criminal suspect bulletins are also available, Mann said.
In the backup system, he said, inspectors have to type in passport numbers and other information instead of simply swiping passports electronically to bring up information on the screen, as happens in the primary system that failed.
"The situation cleared up as of late last night," said Marc Henderson, an MIA spokesman. "Everything is back to the typical daily routine."
Mann said cooperation among Customs and Border Protection, the aviation department, the airlines and passengers made the disruption more bearable.
Customs and Border Protection officials said the failure had affected all U.S. ports of entry.
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But Knocke said Friday that only international airports were affected, including Miami, JFK, Dallas-Fort Worth, Los Angeles, San Francisco, Houston and Laredo, Texas