MDL_777 From United States of America, joined Aug 2001, 267 posts, RR: 0 Posted (14 years 2 weeks 2 days 21 hours ago) and read 2458 times:
While spotting at my local airport, I've noticed some strange smudge-like markings on the left side of many of the aircraft. It's really apparent on aircraft with dark paint schemes. Here's an example:
I've noticed it mostly on the 737's, but it's also evident on some of the A319's and A320's that I've seen as well. It's kind of odd - the "smudges" are always around the cockpit window, and the first passenger window, and always on the left side. I was curious if anyone had an explanation for this. Does it have to do with cabin pressurization?