The ornamental design for a plane, as shown and described.
FIG. 1 is a top, rear and left side perspective view of a plane, showing our design; and
FIG. 2 is a top, front and right side perspective view thereof; and,
FIG. 3 is a front view thereof.
The phantom-line and/or broken-line depictions in FIGS. 1 and 2 are shown for environmental and illustrative purposes only, and form no part of the claimed design of the present invention. Also, the exhaust rings shown in FIGS. 1 and 2 are shown for environmental and illustrative purposes only, and form no part of the claimed design of the present invention.