WASHINGTON — All the Navy recovered after Lt. Nathan Poloski’s fighter jet collided in midair with another Navy jet on a training mission in the western Pacific in September were his flight helmet and a few bits of debris. The 26-year-old pilot, who was deployed aboard the aircraft carrier Carl Vinson, died one month before the ship steamed into the Persian Gulf and began launching combat missions against the Islamic State.

Lieutenant Poloski’s body and his F/A-18C Hornet were never found in waters nearly three miles deep. The other Hornet pilot was rescued after ejecting from his burning jet. Navy officials concluded that the crash shortly after takeoff was a tragic accident and assigned no blame.

Since the Sept. 11, 2001, terrorist attacks, the United States has focused largely on the thousands of American casualties suffered in the grinding ground combat in Iraq and Afghanistan. But while tiny in comparison, the number of fatal aviation accidents — in combat and in training — illustrates the everyday hazards facing American military pilots and aircrews around the globe.

The Navy’s investigation into Lieutenant Poloski’s fatal crash — a copy of which was obtained by The New York Times through a Freedom of Information Act request after it was completed last month — reveals new details about the collision as well as larger insights into the dangerous business of carrier operations, even when a ship and its aerial armada are not at war.