An Unanswered Question

We spent a recent evening in our backyard enjoying a bonfire and doing some star gazing.  From time to time, we would see a plane fly overhead and wonder about it.  Where was it coming from and going to?  Just for fun, we would imagine all sorts of destinations.

But then we started to ponder the science of it.  We saw at least a half dozen planes that night and they were all little more than dots in the sky, so we had to assume they were flying at cruising altitude, approximately 30,000 feet.  The closest major airport is about 60 miles away.  Would a plane have climed that high in that distance or were the planes we were seeing coming from a more distant airport?  This led to the biggest question of the evening.  How far away, in land miles, could a plane be seen? 

Let me clarify.  Let's imagine there was a super bright light that shined from the bottom of the plane, back to the ground.  We can agree that the light would mark a specific location and we could say that the plane was directly over that location, correct?  So the question is, how far from that location would you be able to see the plane in the sky?  One hundred miles, five hundred miles, one thousand miles?  From my home in Michigan, could I see a plane flying over Ohio?  I'm sure there is a scientific formula to figure this out, but I haven't researched it, yet.

So, friends, what do you think?  How far away, in land miles, could a plane (flying at 30,000 feet) be seen from your backyard?  The only prize awarded will be bragging rights, but think how smart you'll feel if you guess correctly* (assuming I can find the answer and determine a winner).

Willoughby

*If you should happen to know the answer already, or have the inclination to research it, please email it to me at thisstopwilloughby@yahoo.com instead of leaving it in the comments.  We don't want to spoil the fun of guessing for everyone else!

**There is still time to enter my Running T-Shirt Giveaway!  Click here for more info.