Abstract: A thrust reverser for a turbofan engine is disclosed in which the pressure of the gases passing through the cold flow air duct act on a downstream segment of the thrust reverser door so that the door is normally biased toward its closed, forward thrust position. This positively eliminates any possibility of the thrust reverser door inadvertently opening into its reverse thrust position. The thrust reverser according to the present invention is thus self-closing regardless of the position and/or functioning of the typical closing and locking mechanisms. The thrust reverser door assembly has internal and external doors separately pivotally attached to the turbofan housing so as to each be movable between closed, forward thrust positions, and opened, reverse thrust positions. A single actuating mechanism may be utilized to move both of the internal and external doors between their respective closed and opened positions.