I nearly dropped my phone when I saw the headline: Hero pilot Captain Sully shares terrifying theory on why DC plane crash happened. If there’s anyone whose opinion I trust about aviation disasters, it’s Chesley “Sully” Sullenberger—the man who famously landed a passenger jet on the Hudson River back in 2009 and saved 155 lives. This time around, Sully’s concerns center on nighttime flights over water, which he suspects might have played a tragic role in the recent collision near Washington, D.C,

According to Sully, the crash that took 67 lives might have stemmed partly from poor visibility when flying over a dark body of water. He noted that fewer ground lights reflecting off water at night can make spotting other aircraft much tougher. As he explained, “All you can see are the lights on them,” which makes determining relative altitude and distance incredibly challenging. Some might question whether an air traffic controller should have stepped in—but as Sully points out, if the pilots see each other and confirm visual contact, the controller can briefly hand over separation duties to them. Sadly, something went horribly wrong.