I should point out that the above is a bit of an oversimplification in
that the distance travelled through the air will be greater than the
ground track distance. So it would take a bit longer than 1 hour to
glide 60 *ground* nm at an *airspeed* of 60 knots. Also, it would take
proportionally longer than 36 minutes to cover the same ground from a
4,000 ft higher altitude. A more rigorous calculation would account
for this.

Regards,

-Doug