Hat tip to Jon Ostrower for posting this amazing photo by Liz Matzelle on FlightBlogger. The photo seems to show the “crowded airspace” over Seattle but according to Liz:
Did some VERY rough math, and I *think* that the C-17 was at around 6,250ft while the CRJ was around 3,000ft. I was at Boeing Field but the CRJ was landing at SeaTac, and I know that the pattern altitude at Boeing Field is 800ft, and it makes sense that the CRJ would be another couple thousand feet above that, so I believe those numbers are at least roughly accurate.
In other words, the photo is completely authentic!