1. A method of planning routes through a 3D image of a tubular organ prior to an actual, follow-on endoscopic procedure, said organ being in the chest region, said method comprising the steps of: computing a model of an airway tree from 3D image data of the organ; receiving information about a target region of interest (ROI) and the follow-on endoscopic procedure associated with the organ; deriving at least one anatomical constraint, at least one endoscopic-device constraint, and at least one procedure-specific constraint from said information, wherein the deriving step comprises constructing a geometric field of view of a virtual endoscope, and requiring at least a portion of the target region of interest (ROI) to be within the geometric field of view extending from the virtual endoscope; automatically computing a plurality of navigable routes to the target region of interest (ROI) and enabling at least one of said routes to be selected based on said anatomical, endoscopic-device, and procedure-specific constraints derived from the information received; and displaying said at least one selected route in conjunction with said model.