A two-part fan cowl comprising two parts (100.1, 100.2), and a system for warning an open state of the fan cowl, wherein each of said parts (100.1, 100.2): at an upper end thereof, is fixed to at least one hinged fitting (101.1, 101.2), and at a lower end thereof, comprises a member (102.1, 102.2) of a latching unit, the non-latched or latched states of which define the open or closed state of such two-part fan cowl, respectively; such that the open state of the two-part fan cowl corresponds to a non-latched state of said latching unit, each part of the fan cowl is left hanged through the respective at least one hinged fitting (101.1, 101.2); wherein: the system comprises at least one device arranged between said parts (100.1, 100.2) of the fan cowl and adapted to exert a force over at least one of the parts thereof spacing such at least one of the parts (100.1, 100.2) apart from the other, thus leaving a predefined gap between them at their lower ends; the at least one device is at least one extensible bumper device secured at its ends to the pair of hinged fittings (101.1, 101.2) of the two-part fan cowl at the upper end; the at least one extensible bumper device further comprises two adaptor fittings, each adaptor fitting securely fixed to one hinged fitting (101.1, 101.2) to which force is exerted allowing the extensible bumper device to relatively move in case only one or both parts (100.1, 100.2) of the two-part fan cowl is separated from the fan; and each adaptor fitting comprises: - a double "U"-shaped plate (12.3) with several attachments means at both ends securely fixed to both one of the hinged fittings (101.1, 101.2) and to an extension plate (12.4), and - such extension plate (12.4) which in turn comprises a rotatable attachment joined to the extensible bumper device at an upper end thereof, is fixed to at least one hinged fitting (101.1, 101.2), and at a lower end thereof, comprises a member (102.1, 102.2) of a latching unit, the non-latched or latched states of which define the open or closed state of such two-part fan cowl, respectively; such that the open state of the two-part fan cowl corresponds to a non-latched state of said latching unit, each part of the fan cowl is left hanged through the respective at least one hinged fitting (101.1, 101.2); wherein: the system comprises at least one device arranged between said parts (100.1, 100.2) of the fan cowl and adapted to exert a force over at least one of the parts thereof spacing such at least one of the parts (100.1, 100.2) apart from the other, thus leaving a predefined gap between them at their lower ends; the at least one device is at least one extensible bumper device secured at its ends to the pair of hinged fittings (101.1, 101.2) of the two-part fan cowl at the upper end; the at least one extensible bumper device further comprises two adaptor fittings, each adaptor fitting securely fixed to one hinged fitting (101.1, 101.2) to which force is exerted allowing the extensible bumper device to relatively move in case only one or both parts (100.1, 100.2) of the two-part fan cowl is separated from the fan; and each adaptor fitting comprises: - a double "U"-shaped plate (12.3) with several attachments means at both ends securely fixed to both one of the hinged fittings (101.1, 101.2) and to an extension plate (12.4), and - such extension plate (12.4) which in turn comprises a rotatable attachment joined to the extensible bumper device the system comprises at least one device arranged between said parts (100.1, 100.2) of the fan cowl and adapted to exert a force over at least one of the parts thereof spacing such at least one of the parts (100.1, 100.2) apart from the other, thus leaving a predefined gap between them at their lower ends; the at least one device is at least one extensible bumper device secured at its ends to the pair of hinged fittings (101.1, 101.2) of the two-part fan cowl at the upper end; the at least one extensible bumper device further comprises two adaptor fittings, each adaptor fitting securely fixed to one hinged fitting (101.1, 101.2) to which force is exerted allowing the extensible bumper device to relatively move in case only one or both parts (100.1, 100.2) of the two-part fan cowl is separated from the fan; and each adaptor fitting comprises: - a double "U"-shaped plate (12.3) with several attachments means at both ends securely fixed to both one of the hinged fittings (101.1, 101.2) and to an extension plate (12.4), and - such extension plate (12.4) which in turn comprises a rotatable attachment joined to the extensible bumper device - a double "U"-shaped plate (12.3) with several attachments means at both ends securely fixed to both one of the hinged fittings (101.1, 101.2) and to an extension plate (12.4), and - such extension plate (12.4) which in turn comprises a rotatable attachment joined to the extensible bumper device