Airport passenger screeners, not a computer glitch, were to blame for the false-alarm evacuations of Midway Airport and two other airports earlier this month, federal authorities said.
Originally, Transportation Security Administration officials said software had faltered in a computer program aimed at making sure screeners are paying attention at airport checkpoints.
But an inspection of those baggage screening machines at Midway, Washington's Dulles International and Miami International airports determined screeners didn't follow proper procedure in logging off the machine during a shift change.
That allowed archived images of weapons -- a grenade at Midway and guns in Washington and Miami -- that were saved for training purposes to be displayed when other bags were scanned, TSA spokeswoman Amy von Walter said.
"For training purposes we allow screeners to keep [images] of real objects for training purposes. Unfortunately in these cases the archived image was pulled up and not closed out." she said.
"When the image was there for the next screener it led to confusion over whether it was a real object."
Von Walter said the screeners to blame for the three evacuations will be sent to "remedial training" as a reminder to close out those archived images. It's unclear if any of them will be disciplined for their mistakes, she said.
Regardless of the cause, Chicago officials say they will still ask the the federal government to reimburse the city for its police response to the Midway evacuation Nov. 15. City officials said they are still trying to determine how much it cost to respond to the evacuation call.
"We feel if this [problem] happened once it was a mistake, but when it happened twice [the FAA] should have notified all airports. We probably would have handled it differently," aviation department spokeswoman Annette Martinez said. "We incurred a lot of cost and inconvenienced passengers traveling that day."
Von Walter said the evacuation call was the right one, saying the TSA has a "duty to investigate any question of a possible weapon on the secure side of an airport."
The TSA, however, is looking to make software improvements aimed at preventing similar occurrences, von Walter said.