Thanks for the analysis, Chris!

The idea that the contractor adds a little bit just to make sure they
don't fall short of what they are aiming for seems plausible. However,
I'll point out that your analysis shows the next most common ending
digit after 1 is 9. Makes me think contractors are missing their goal
by one foot almost as frequently as they are overshooting it by one
foot.

I don't know anything about the engineering of runways, but it would
come as a surprise to me that modern methods (laser range finding,
GPS, etc.) couldn't pin down a runway length to within several inches.
The fact that there are so many that end in 0 would seem to indicate
that contractors can make a runway the exact length they want to.

It would be interesting to see the runway specifications as spelled
out in the original construction contract.

"Wayhoo.com" wrote in message ...
Can anyone explain why runway lengths are sometimes "X thousand and
ONE feet" in length? I was just looking through a list of Iowa's
approximately 110 airports and 7 of them have runways that are "X
thousand and one feet" long.

Do runway manufacturing companies offer special deals like "Buy 5,000
feet of runway, get your next foot free!!!"

There's got to be a logical explanation - anyone know it?

According to FAA data, here is a count of runways grouped by the last digit
of the Runway Length.

Sorted by frequency
digit, count, %
0, 4333, 57.6%
5, 582, 7.7%
1, 549, 7.3%
9, 385, 5.1%
2, 379, 5.0%
8, 311, 4.1%
3, 274, 3.6%
7, 241, 3.2%
4, 234, 3.1%
6, 230, 3.1%

There does seem to be a statistically high percentage of runways with an
extra foot. Perhaps it's the 'fudge factor' the construction contractor
used to ensure they met specifications.

Chris
http://wayhoo.com/