Propulsion unit for an aircraft, comprising a turbine engine with a longitudinal axis parallel to a longitudinal direction of said turbine engine, and an engine mounting device designed to be added laterally on an aircraft structure, said mounting device comprising a rigid mounting structure with a proximal end that will be connected to the aircraft structure and with a distal end arranged facing the turbine engine, said rigid mounting structure supporting connecting means (28, 134, 140a, 140b, 146, 152, 172a, 172b, 182, 158a, 158b, 158c) connecting said turbine engine to said rigid mounting structure, in which: - said connecting means comprise at least one arch (62, 64) with a proximal end connected to said rigid mounting structure and an opposite distal end; - said arch (62, 64) being concave towards said longitudinal axis; - said proximal end and distal end of said arch (62, 64) extend on each side of a longitudinal plane containing said longitudinal axis and that will extend vertically when said propulsion unit is fitted on an aircraft parked on the ground; and - when said arch (62, 64) is seen in a sectional view on a transverse plane orthogonal to said longitudinal axis, a first half-line and a second half-line delimit an angular sector with an angle (θ1) of between 45 degrees and 120 degrees, wherein the first half line starts from said longitudinal axis and passes through the distal end of said arch (62, 64), and the second half-line starts from said longitudinal axis, is contained in said longitudinal plane, and intercepts said arch (62,64), said propulsion unit being characterised in that said connecting means comprise a distal connecting element connecting the turbine engine to a distal mounting part (96c, 122b) of said arch (62, 64) and arranged on the same side as said distal end of said arch relative to said longitudinal plane, said distal mounting part (96c, 122b) being arranged such that when said arch (62, 64) is seen in a sectional view on said transverse plane, said distal mounting part (96c, 122b) extends outside an angular sector defined such that: - the longitudinal axis is its vertex, - it forms an angle (θ2) equal to between 25 degrees and 100 degrees, - it extends from said second half-line towards said distal end of said arch (62,64). - said connecting means comprise at least one arch (62, 64) with a proximal end connected to said rigid mounting structure and an opposite distal end; - said arch (62, 64) being concave towards said longitudinal axis; - said proximal end and distal end of said arch (62, 64) extend on each side of a longitudinal plane containing said longitudinal axis and that will extend vertically when said propulsion unit is fitted on an aircraft parked on the ground; and - when said arch (62, 64) is seen in a sectional view on a transverse plane orthogonal to said longitudinal axis, a first half-line and a second half-line delimit an angular sector with an angle (θ1) of between 45 degrees and 120 degrees, wherein the first half line starts from said longitudinal axis and passes through the distal end of said arch (62, 64), and the second half-line starts from said longitudinal axis, is contained in said longitudinal plane, and intercepts said arch (62,64), - the longitudinal axis is its vertex, - it forms an angle (θ2) equal to between 25 degrees and 100 degrees, - it extends from said second half-line towards said distal end of said arch (62,64).