An air cushion is a space containing air under pressure, generally placed under a vehicle or an object to be moved. This air must be constantly renewed, either by a fan or by the movement of the vehicle as it "bleeds" from the relevant peripheries about the vehicle.

The flow of air leaving the hovercraft air cushion is directly proportional to the craft peripheral length and hovercraft height. In order to reduce the flow and the power required to maintain it, flexible skirts were developed, allowing the hovercraft to maintain a reasonable hover height with a few centimetres air escape gap and minimal "bleed".

Below are some of the common style "skirts" employed by various hover craft over the years.

used on:
   Sedam N.101
   Sedam N.102
   Sedam N.300
   Sedam N.500
   Be11 Carabao
   Aerojet Manta

used on:
   SR.N1
   SR.N2

used on:
   Vickers

used on racing hovercraft for higher speeds

used on:
   SR.N2
   SR.N3
   SR.N5
   SR.N6

used on:
   SR.N3
   SR.N4
   SR.N4 Mk.2
   SR.N5s
   SR.N6s
   BH.7

used on:
   HD2
   VT1
   EM2