U.S. airports were warned about possible screening equipment problems Friday after a software glitch knocked out the metal detectors, x-ray machines and security checkpoint computers at Nashville International Airport for five hours Friday.

"The situation has reverberated across the nation," said David Beecroft, who oversees security operations at the airport for the federal Transportation Security Administration.

All international airports in the country were alerted because the company that supplies the computer software at Nashville also serves several other airports, Beecroft said. He didn't immediately have the name of the contractor.

None of the computers, x-ray machines or metal detectors at the Nashville airport's two screening checkpoints were operating when security operations were scheduled to open for the day at 3:30 a.m., Beecroft said.

TSA employees searched bags by hand and used hand-held metal detector wands to screen passengers while the system was down.

Lines of hundreds of passengers snaked outside the terminal and into the parking areas because of the delays. About 9,000 to 11,000 people use the airport every day, but airport spokeswoman Lynne Lowrance said air traffic Friday was expected to be heavier than usual with families traveling for spring break.

Many people were missing flights because some planes waited only 15-20 minutes before leaving the gate, Lowrance said.

"We did delay some of our flights out this morning in an effort to get as many people on their flights as possible. Some flights left as much as 45 minutes late," Marilee McInnis, spokeswoman for Southwest Airlines said.

Southwest is the Nashville airport's biggest carrier, and McInnis said the delays would affect flights in other cities Friday.

American Airlines reported flight delays of 26 minutes to an hour for four flights, spokesman Tim Wagner said.