The Clark McAlpine Trail along the West side of the airport was built by the Port of Friday Harbor, with some assistance by the Trails Committee and Boy Scout Troop 90. It begins on West Spring Street just west of San Juan Office Supply and continues through airport property and near Skagit Valley College. Part of it is a narrow path along the airport fence and through the woods, and it loops back on a paved road open for emergency vehicles only (walkers welcome) that goes all the way to Shelter Road south of the airport.

In 2005 the Trails Committee and airport staff added a loop trail south of Shelter Road connecting to Cattle Point Road near its intersection with Golf Course Road.