Safety officials remain mystified why windshields cracked on at least 14 planes at Denver International Airport on Friday.
"We are not discounting anything," said Federal Aviation Administration spokesman Allen Kenitzer, whose agency is among those investigating the incidents. "We believe it is very remarkable to have this number of events in the same area at the same time."
The National Transportation Safety Board will have a glass specialist from its structures division examine 22 damaged front and side windshields that were removed from the affected planes, said NTSB air-safety investigator Jennifer Kaiser.
The cracking occurred over a 1 1/2 hour period on Friday afternoon, Kaiser said. Some planes were taking off, some were landing and some were parked at various locations on DIA's airfield.
DIA was experiencing highly variable weather at the time of the incidents, with high winds, rapid temperature changes and some snow, Kaiser said.
NTSB is looking at whether a pressure change may have contributed, she said.
DIA spokesman Chuck Cannon said airport operations and maintenance employees could offer no explanation for the windshield problems.
"It's baffling," he said.
Commuter carrier SkyWest Airlines reported nine of its planes suffered windshield cracks, and Frontier Airlines officials said four of its aircraft suffered similar damage.
One plane from Great Lakes Airlines encountered the problem as well, Kaiser said.
SkyWest, which operates about 152 departures a day from Denver, halted its DIA operations for 1 1/2 hours after the windshield cracks were discovered.
DIA was buffeted by winds that exceeded 50 mph at times on Friday, officials said. Initial reports suggested the windshield damage might have been caused by chunks of ice or other blowing debris.
Yet that would likely have damaged other parts of a plane's exterior, and SkyWest spokeswoman Marissa Snow said no additional damage was found on her company's aircraft.
The NTSB's Kaiser confirmed that there were no reports of impact from flying debris.
Frontier reported that cracks were noticed by employees on two of the company's planes while they were parked at gates and hooked up to an airport power source, leading to speculation that a power surge might have led to the unusual cracking of the windshields, which have electronic heating elements.
However, the SkyWest planes that suffered windshield cracks were never hooked up to a DIA power source, and the planes were in the process of taking off or landing when the problem developed, Snow said.
The FAA's Kenitzer said the airlines handled the windshield problem "in a proper manner and there were no safety problems with the incident."
He added: "We will find an answer."
News stories provided by third parties are not edited by "Site Publication" staff. For suggestions and comments, please click the Contact link at the bottom of this page.