Beech C99 accident near Londonderry, New Hampshire, January 26, 2024

The NTSB's narrative final · quoted from the NTSB record

The weather about the time of departure included visibility of 3 miles in rain and mist, a broken ceiling at 1,000 ft, and an overcast ceiling at 2,400 ft. The pilot stated that during the initial climb, he heard a loud “pop.” The left door/hatch appeared to be partially open, so he grabbed it with his left hand. The door then opened completely while he was still holding on to it, injuring his left hand. He reached up with his right hand and hung on to the door with both hands but was beginning to be pulled out of his seat, so he let go and, shortly after, the door completely separated from the airplane. After the door departed, the airplane went through a series of unusual attitudes as the pilot attempted to return to the departure airport. He did not recall anything after the last unusual attitude. Postaccident examination of the wreckage did not reveal any preimpact mechanical malfunction. The cockpit door was found about 10 miles from the main wreckage. The airplane was also equipped with a portable ladder for pilot entry, which secured to the fuselage under the cockpit door, and was supposed to have been stowed inside the cockpit before takeoff. Although the pilot reported that he checked that the door before takeoff, the portable ladder was found outside and aft of the cockpit, consistent with the pilot forgetting to secure the portable ladder inside the cockpit. He likely also failed to ensure that the cockpit door was secured before takeoff.

The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.