<p>WASHINGTON &mdash; The pilots of two Alaskan sightseeing planes that collided in midair couldn’t see the other aircraft because airplane structures or a passenger blocked their views, and they didn’t get electronic alerts about close aircraft because safety systems weren’t working properly.</p>
<p>That’s what the staff of the National Transportation Safety board found in their investigation of the May 2019 crash, which killed six people.</p>
<p>The board is meeting Tuesday in Washington to determine a probable cause of the crash and make recommendations to prevent it from happening again. </p>
<p>Mountain Air Service pilot Randy Sullivan and his four passengers, and a passenger in a plane owned by Taquan Air were killed. Ten people suffered injuries when the aircraft converged at 3,350 feet (1,021 meters).</p>
<p>The Ketchikan-based floatplanes carrying passengers from the same cruise ship, the Royal Princess, were returning from tours of Misty Fjords National Monument.</p>
<p>Mountain Air’s single-engine de Havilland DHC-2 MK 1 Beaver and Taquan’s larger turboprop de Havilland DHC-3 Otter collided just after noon over the west side of George Inlet.</p>