On May 20, 2017, about 1459 Pacific daylight time, the canopy of an experimental Extra Flugzeugbau EA 300/S airplane, N68PW, departed from the airplane during takeoff roll from Eastern Oregon Regional Airport (PDT) Pendleton, Oregon. The private pilot was not injured. The airplane was substantially damaged to the canopy and wing. The airplane was registered to Precision Aerosports LLC and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan had been filed for the local flight that was originating at the time. During a telephone interview with a National Transportation Safety Board investigator, the pilot stated that shortly after the start of the takeoff roll, the canopy began to lift up and separate from the airplane. The airplane subsequently veered left, exited the runway, and struck an airport runway sign, during the aborted takeoff. The pilot reported that he did not remember checking that the canopy was locked and was fairly sure it was not latched. The pilot reported no mechanical malfunction or failure that would have precluded normal operation. Postaccident examination of the airplane revealed no anomalies with the canopy, canopy attachment bolts, mounting bolt holes, latches, or locking mechanism. Additionally, no cracking or corrosion was observed. The canopy is manufactured in one section and is operated manually by the pilot and opens by lifting it to the right. The canopy has fore and aft interior locking handles, located on the left side of the canopy frame, that must be squeezed together to unlock the canopy. Both locking handles must be in the outward position when locked. A placard located near the locking handles of the cockpit indicates the unlock and locked positions. The airplane Pilot's Operating Handbook contains a checklist item, to close and lock the canopy, both in the Before Starting Engine, and the Taxi, checklists. Further, a caution about the canopy states: "handles of the lock mechanism must be in opposite position indicated with a red line on the canopy frame. Check gap between canopy frame and fuselage fairing!"