An aircraft comprising: - a fuselage with a first longitudinal extension axis between a nose and a tail portion opposite along said first longitudinal extension axis; - a pair of half-wings extending in a cantilever fashion from respective opposite sides of said fuselage and transversely to said first longitudinal extension axis; - a pair of nacelles; and - a pair of rotors; each said rotor comprising, in turn,: - a motor; - a drive shaft rotatable about a second axis; - a hub dragged, in use, into rotation by said drive shaft; - a plurality of blades, which are articulated on said hub; said aircraft further comprising a transmission (!0) which transmits, in use, the power from said motor to said drive shaft; said transmission being a gear reducer and comprising: - an external support casing; - an input shaft (12, 12') supported by said external casing and connected to said motor; and - an output shaft supported by and coupled to said external casing by means of a second coupling assembly, which comprises a rolling bearing, said output shaft being connected to said drive shaft; said external casing comprising a support element (16; 16'); said input shaft (12; 12') rotating, in use, about a third axis (E, E'); said transmission comprising a first coupling assembly for coupling said input shaft to said casing; said first coupling assembly comprising a pair of oblique rolling bearings (17; 17') mounted so as to couple said input shaft (12; 12') to said support element (16; 16') in a rotating manner about said axis (E, E'); said rolling bearings (17; 17') comprising: - respective first races (18, 19; 18', 19') cooperating radially in contact with a first component (16, 12; 16', 12') defined by one from said support element (16; 16') and said input shaft (12; 12'); - respective second races (19, 18; 19', 18') cooperating radially in contact with a second component (12, 16; 12', 16') defined by the other from said support element (16; 16') and said input shaft (12; 12'); and - respective pluralities of rolling elements (20; 20') adapted to roll on said first and said second races (18, 19; 18' 19'; 19, 18; 19', 18'); characterized by further comprising a pair of preloaded elastic members (21; 21'), which couple said first races (18, 19; 18', 19') to said first component (16, 12; 16', 12') respectively, axially and in an elastically yielding manner; wherein said couple of elastic members (21; 21') is arranged axially between said first races (18, 19; 18', 19'); wherein said first component (16, 12; 16', 12') defines a pair of first shoulders (33; 33') arranged axially between said pair of preloaded elastic members (21; 21'); said preloaded elastic members (21; 21') coupling said first races (18, 19; 18', 19') to said first shoulders (33; 33') respectively, in an elastically yielding manner in an axial direction; wherein said first component (16, 12; 16', 12') defines a pair of second shoulders (35; 35') respectively axially facing said first races (18, 19; 18', 19'), so as to define respective axial end-stops for said first races (18, 19; 18', 19'); said first races (18, 19; 18', 19') being configured to float, in use, along said third axis (E, E') in response to the application of an axial load on said first component (16, 12; 16', 12'). - a fuselage with a first longitudinal extension axis between a nose and a tail portion opposite along said first longitudinal extension axis; - a pair of half-wings extending in a cantilever fashion from respective opposite sides of said fuselage and transversely to said first longitudinal extension axis; - a pair of nacelles; and - a pair of rotors; - a motor; - a drive shaft rotatable about a second axis; - a hub dragged, in use, into rotation by said drive shaft; - a plurality of blades, which are articulated on said hub; - an external support casing; - an input shaft (12, 12') supported by said external casing and connected to said motor; and - an output shaft supported by and coupled to said external casing by means of a second coupling assembly, which comprises a rolling bearing, said output shaft being connected to said drive shaft; said external casing comprising a support element (16; 16'); - respective first races (18, 19; 18', 19') cooperating radially in contact with a first component (16, 12; 16', 12') defined by one from said support element (16; 16') and said input shaft (12; 12'); - respective second races (19, 18; 19', 18') cooperating radially in contact with a second component (12, 16; 12', 16') defined by the other from said support element (16; 16') and said input shaft (12; 12'); and - respective pluralities of rolling elements (20; 20') adapted to roll on said first and said second races (18, 19; 18' 19'; 19, 18; 19', 18');