A gas turbine engine for an aircraft comprising: an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor; a fan located upstream of the engine core, the fan comprising a plurality of fan blades, each fan blade having a pressure surface and a suction surface; and a gearbox that receives an input from the core shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the core shaft, wherein: for a given cross-section through the fan blade each fan blade has: a camber line defined by the midpoint between its pressure surface and its suction surface, with a true chord being defined as the distance along the camber line between a leading edge and a trailing edge of the fan blade; a covered passage defined as the portion of the cross-section between the trailing edge and a line passing through a point on the suction surface that is closest to the leading edge of a neighbouring fan blade and the leading edge of that neighbouring fan blade; a covered passage length defined as the distance along the camber line that is in the covered passage; and a covered passage percentage defined as the covered passage length as a percentage of the true chord, characterized in that: for all cross-sections through each fan blade for which the covered passage percentage is between 40% and 70%, the change in angle of the camber line between the leading edge (α1) and the point on the camber line that corresponds to the start of the covered passage (α2) satisfies: α 2 − α 1 ≥ 6 + covered passage percentage − 35 9 degrees an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor; a fan located upstream of the engine core, the fan comprising a plurality of fan blades, each fan blade having a pressure surface and a suction surface; and a gearbox that receives an input from the core shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the core shaft, wherein: for a given cross-section through the fan blade each fan blade has: a camber line defined by the midpoint between its pressure surface and its suction surface, with a true chord being defined as the distance along the camber line between a leading edge and a trailing edge of the fan blade; a covered passage defined as the portion of the cross-section between the trailing edge and a line passing through a point on the suction surface that is closest to the leading edge of a neighbouring fan blade and the leading edge of that neighbouring fan blade; a covered passage length defined as the distance along the camber line that is in the covered passage; and a covered passage percentage defined as the covered passage length as a percentage of the true chord, characterized in that: for all cross-sections through each fan blade for which the covered passage percentage is between 40% and 70%, the change in angle of the camber line between the leading edge (α1) and the point on the camber line that corresponds to the start of the covered passage (α2) satisfies: α 2 − α 1 ≥ 6 + covered passage percentage − 35 9 degrees for a given cross-section through the fan blade each fan blade has: a camber line defined by the midpoint between its pressure surface and its suction surface, with a true chord being defined as the distance along the camber line between a leading edge and a trailing edge of the fan blade; a covered passage defined as the portion of the cross-section between the trailing edge and a line passing through a point on the suction surface that is closest to the leading edge of a neighbouring fan blade and the leading edge of that neighbouring fan blade; a covered passage length defined as the distance along the camber line that is in the covered passage; and a covered passage percentage defined as the covered passage length as a percentage of the true chord, characterized in that: for all cross-sections through each fan blade for which the covered passage percentage is between 40% and 70%, the change in angle of the camber line between the leading edge (α1) and the point on the camber line that corresponds to the start of the covered passage (α2) satisfies: α 2 − α 1 ≥ 6 + covered passage percentage − 35 9 degrees a camber line defined by the midpoint between its pressure surface and its suction surface, with a true chord being defined as the distance along the camber line between a leading edge and a trailing edge of the fan blade; a covered passage defined as the portion of the cross-section between the trailing edge and a line passing through a point on the suction surface that is closest to the leading edge of a neighbouring fan blade and the leading edge of that neighbouring fan blade; a covered passage length defined as the distance along the camber line that is in the covered passage; and a covered passage percentage defined as the covered passage length as a percentage of the true chord, characterized in that: for all cross-sections through each fan blade for which the covered passage percentage is between 40% and 70%, the change in angle of the camber line between the leading edge (α1) and the point on the camber line that corresponds to the start of the covered passage (α2) satisfies: α 2 − α 1 ≥ 6 + covered passage percentage − 35 9 degrees