and positively deploy while the deployable air inlet duct of this invention is especially applicable to cruise missiles it may be used in any suitable application for example a deployable inlet would be useful to direct air to a small jet engine powering an emergency power unit in large aircraft also a small emergency jet engine on a sailplane or glider could advantageously utilize a deployable inlet giving low drag when retracted during normal operation and rapid positive deployment in an emergency the arrangement of the inflatable inlet duct in the stowed and deployed positions is shown in fig2 5 as seen in fig2 deployable inlet duct 18 when collapsed is stowed in a cavity entirely within the outline of missile 10 the stowed inlet duct 18 is closely surrounded by fuel tanks 20 and connects directly to permanent internal duct 22 to direct air to a jet engine schematically indicated at 24 duct 18 is shown in fig4 after release of cover 19 which acts as a restraining means and inflation of the inflatable outer duct wall as described below cover 19 is held in place by conventional latch means not shown which can be rapidly released so that cover 19 will fall away duct 18 includes leading edge 26 which together with duct plate 28 forms a scoop shaped inlet for admitting air which passes through the.