The ornamental design for an aircraft, as shown and described.
FIG. 1 is a front perspective view of the portion of an aircraft showing our new design;
FIG. 2 is a magnified view thereof;
FIG. 3 is a front view thereof, the back view forming no part of the claimed design;
FIG. 4 is a first side view thereof;
FIG. 5 is a second side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is an exploded perspective view with portion shown removed from aircraft for clarity of disclosure thereof;
FIG. 8 is a second exploded perspective view with portion shown removed from aircraft for clarity of disclosure thereof; and,
FIG. 9 is a magnified top view thereof.
The short even length broken lines illustrate portions of an aircraft that form no part of the claimed design. The long even length broken line illustrates a portion to be magnified in a separate view. The single dash and single dot broken line represents a boundary of the claimed design but forms no part thereof.