Mxsmanic wrote
I was under the impression that just about nothing could crack an
airliner windshield short of a transonic brick, but I may be wrong.
On smaller aircraft, I don't know. I suppose they have some sort of
regular safety glass for the windshields, but less fancy than that of
high-flying jets (?).

Of course these jet windshields are heated to provide the middle layer
of plastic with some flexibility to resist shattering in case of a bird
strike at low temps. Should the heating system be turned off and cold-
soaking occur(electrical bus turned off for trouble-shooting perhaps),
Boeing had a procedure for re-heating the windshield at very low temps
to prevent thermal shock from cracking the glass layers. This involved
cycling the power switches ON-OFF at one minute intervals for several
minutes. Sounds to me as if the temps at DEN were quite low and the flight
crews just turned the windshield heat ON and forgot about it.

Just one possibility of course.....

Bob Moore
ATP B-727 B-707
PanAm (retired)