GROUND EFFECT:
Also known as the "wing in ground effect,"
it happens as an aircraft approaches the ground. As the plane
approaches the ground,
the plane experiences
a dramatic drop in drag. This effect starts when the aircraft is
one wingspan off the ground and increases until the most noticable
effects are noticed at one
half the wingspan. This effect has cause trouble for new pilots, and
has been taken advantage of by the Russians
as they developed an
aircraft that is made to fly close to the ground. This aircraft is
called the Ekranoplan as is pictured below.
http://en.wikipedia.org/wiki/File:A-90_Orlyonok_1.JPG