​​​On May 13, 2019, about 1221 Alaska daylight time, a float-equipped de Havilland DHC-2 (Beaver) airplane, N952DB, and a float-equipped de Havilland DHC-3 (Otter) airplane, N959PA, collided in midair about 8 miles northeast of Ketchikan, Alaska. The DHC-2 pilot and four passengers sustained fatal injuries. The DHC-3 pilot sustained minor injuries, nine passengers sustained serious injuries, and one passenger sustained fatal injuries. The DHC-2 was destroyed and the DHC-3 sustained substantial damage. The DHC-2 was registered to and operated by Mountain Air Service LLC, Ketchikan, Alaska, under the provisions of Title 14 Code of Federal Regulations (CFR) Part 135 as an on-demand sightseeing flight. The DHC-3 was registered to Pantechnicon Aviation LTD, Minden, Nevada, and operated by Venture Travel, LLC, dba Taquan Air, Ketchikan, Alaska, under the provisions of Part 135 as an on-demand sightseeing flight. Visual meteorological conditions prevailed in the area at the time of the accident.The purpose of both flights was to transport passengers to Ketchikan from the Misty Fjords National Monument area in Alaska, USA. Both flights were converging on a scenic waterfall before returning to the Ketchikan Harbor Seaplane Base.At 12:17:15, the DHC-3 was about level at 4,000 ft mean sea level (msl) on a track of 225°, and the DHC-2 was 4.2 nautical miles south of the DHC-3, climbing through 2,800 ft msl, on a track of 255°. About 12:19, the DHC-3 started a descent from 4,000 ft msl, and the DHC-2 was at 3,175 ft msl and climbing. During the next 1 minute 21 seconds, the DHC-3 continued to descend on a track between 224° and 237°, and the DHC-2 leveled out at 3,350 ft msl on a track of about 255°. The airplanes collided at 12:21:14 at an altitude of 3,350 ft msl, 7.4 nm northeast of Ketchikan Harbor.The DHC-3 pilot stated to the NTSB that the flight from the Misty Fjords area had proceeded normally, and he had descended and was maneuvering the airplane to show passengers a wa