FOD Caused Cracked Windshields

On February 16, numerous freak incidents of cracked aircraft windshields at Denver International Airport were reported. The cracked windshields were on 14 aircraft of various aircraft type operated by three different carriers. Six aircraft experienced the cracking during takeoff, another just after landing, two upon taxiing to the terminal after landing, and three while they were sitting at their gates. Wind speeds that day were gusting up to 48 miles per hour. I have to imagine that all those cracked windshields caused many engineers and mechanics to scratch their heads as they tried to figure out the cause. The NTSB still hasn't issued a final report on the incidents, but Denver-based NTSB investigator Jennifer Kaiser, who led the probe into these incidents, has commented on the likely cause of the cracks. A February 28 article in the Denver Post by Jeffrey Leib says that Kaiser attributes the damage to FOD. So, what kind of FOD is Kaiser talking about? Hail? Hardware on the ramp thrown into the windows? Bird strikes? Rocks? None of the above. Believe it or not, it was sand. In the article, Kaiser says it is possible that sand that was put down on the airport's runways and taxiways during December and January snow storms were blown into the windshields that windy February day. Microscopic analysis of the windows showed that fine particles caused pitting in the windows. The pitting in turn caused the cracking. So, case solved? Maybe not. Investigators were not able to determine with certainty what debris caused the damage because there were no transfer marks from the material onto the windshields. It is hard to imagine that blowing sand can cause aircraft windshields to crack. If it can, I am curious -- how were all the other aircraft that were at the airport that day affected by the sand? Were they also damaged by the sand FOD? Will that damage eventually lead to more freak incidents of cracked windshields? You can click here to read the full Denver Post article. Thanks for reading. Joe