reply to post by JonInMichigan
A lot of contrails, that lasted for some time, apparently.
First, I looked up on an aeronautical chart (you can too) and your location is very near the Salem VORTAC. That facility has, as part of the normal
Jet Airway route structure, "Jet 70" airway, that runs almost precisely West/East, in your location.
I don't know how to grab a screenshot, so you'll have to go to www.skyvector.com...
, and when the page loads, look for the box, upper left
corner to input a location. KDTW (for Detroit Wayne) works fine. Click 'Go", and a VFR Sectional will load. That is for low-altitude reference,
so you want to find a button labeled "Enroute H-10", that brings up the High-Altitude (over 18,000 feet) chart. So, you will see the Airways, and
I'm guessing (the winds aloft can be checked) that there was a fairly strong, slightly angled north or south wind, at altitude. Angled to the
magnetic course of the Airway. So, as the airplanes fly past, reference to points located on the ground (the Airway Route structure) their contrails
will drift along, with the prevailing winds, after being formed. The regularity is accounted for by the fact that the airplanes likely had a certain
regular spacing, when laying down the contrails, as they flew by. Remember, too, that just a few thousand feet vertically, separating those different
contrails, will be hard to gauge from seven miles beneath them.
Found this link to aviation winds aloft for time period...closest to your area is Muskegon, for reporting and forecasting purposes. The winds cover
broad areas, and localized differences are minor.
Wind direction was forecast 280 degrees TRUE (not magnetic, as the Aeronautical charts are oriented to). And, you can see at 34,000 feet, about 96
MPH velocity. Magnetic Variation in your area is about 5 degrees west, so the winds magnetic direction would be about 285. That gives them about a
ten degree angle across the Airway...and made the contrails space so evenly, as you saw.