The ornamental design for an aircraft, as shown and described.
FIG. 1 is a perspective view of a first embodiment of an aircraft showing my new design;
FIG. 2 is a left side view of the aircraft as shown in FIG. 1 showing our new design, which is a mirror image of the right side view;
FIG. 3 is a top view of the aircraft as shown in FIG. 1 showing our new design;
FIG. 4 is a bottom view of the aircraft as shown in FIG. 1 showing our new design;
FIG. 5 is a front view of the aircraft as shown in FIG. 1 showing our new design;
FIG. 6 is a back view of the aircraft as shown in FIG. 1 showing our new design;
FIG. 7 is a perspective view of a second embodiment of an aircraft showing our new design;
FIG. 8 is a left side view of the aircraft as shown in FIG. 7 showing our new design, which is a mirror image of the right side view;
FIG. 9 is a top view of the aircraft as shown in FIG. 7 showing our new design;
FIG. 10 is a bottom view of the aircraft as shown in FIG. 7 showing our new design;
FIG. 11 is a front view of the aircraft as shown in FIG. 7 showing our new design; and,
FIG. 12 is a back view of the aircraft as shown in FIG. 7 showing our new design.
The broken line showing of portions of an aircraft is included for the purpose of illustrating environmental structure and forms no part of the claimed design.