An inertial particle separator (100;200) configured for communicating with an engine inlet of an aircraft engine having an axis, the inertial particle separator (100;200) comprising: a main duct (22;122) having an inlet fluidly connected to an environment outside of the aircraft engine, and for receiving an airflow from the environment along a first direction, and an outlet configured for being fluidly connected to the engine inlet, the main duct (22;122) having a first side facing away from the axis and a second side opposed to the first side and facing toward the axis; a bypass duct (24;124) stemming from the main duct (22;122) between the inlet and the outlet, the bypass duct being fluidly connected to the main duct (22;122); and a splitter defined by an intersection of the main duct (22;122) and the bypass duct (24;124), the splitter having a leading edge, characterised in that: the second side of the main duct (22;122) at the inlet extends from the inlet along a second direction defining an angle (α) of at most 45 degrees with the first direction; the main duct (22;122) has a radially outward-most section between the inlet and the splitter, the radially-outward most section having a height extending from the first side to the second side and a width, and W1/H1≥0.5; a length from the second side to the first side, from the radially-outward most section along a direction parallel to the second direction, is at least as great as the height of the main duct (22;122) at the radially outward-most section; a height of the main duct (22;122) from the leading edge of the splitter to the second side of the main duct (22;122) is at most four times the height of the main duct (22;122) at the radially outward-most section; and a height of the bypass duct (24;124) from the first side at an end of the length to the leading edge is at least 20% of the height of the main duct (22;122) at the radially outward-most section. a main duct (22;122) having an inlet fluidly connected to an environment outside of the aircraft engine, and for receiving an airflow from the environment along a first direction, and an outlet configured for being fluidly connected to the engine inlet, the main duct (22;122) having a first side facing away from the axis and a second side opposed to the first side and facing toward the axis; a bypass duct (24;124) stemming from the main duct (22;122) between the inlet and the outlet, the bypass duct being fluidly connected to the main duct (22;122); and a splitter defined by an intersection of the main duct (22;122) and the bypass duct (24;124), the splitter having a leading edge, the second side of the main duct (22;122) at the inlet extends from the inlet along a second direction defining an angle (α) of at most 45 degrees with the first direction; the main duct (22;122) has a radially outward-most section between the inlet and the splitter, the radially-outward most section having a height extending from the first side to the second side and a width, and W1/H1≥0.5; a length from the second side to the first side, from the radially-outward most section along a direction parallel to the second direction, is at least as great as the height of the main duct (22;122) at the radially outward-most section; a height of the main duct (22;122) from the leading edge of the splitter to the second side of the main duct (22;122) is at most four times the height of the main duct (22;122) at the radially outward-most section; and a height of the bypass duct (24;124) from the first side at an end of the length to the leading edge is at least 20% of the height of the main duct (22;122) at the radially outward-most section.