Boeing this week rolled out its first 737 without eyebrow windows, the four small windows above the front windshield. In the past the eyebrow windows helped provide better crew visibility, but today's advanced navigation systems have made those windows obsolete. The design change reduces airplane weight by 20 pounds and eliminates approximately 300 hours of periodic inspections per airplane. Retrofit kits to cover eyebrow windows will be available mid-2006 for the in-service 737 fleet.
What's in the retrofit kit? Four pieces of metal, a bag of rivets, and a little hammer to smash in the windows?
But seriously, aircraft are routinely patched up when someone punches a hole in them with a forklift, so I'm sure it would not be that much of a problem for an airline to remove the windows and patch up the holes. So why didn't anyone do it?