Of the 12 men who flew aboard the Enola Gay the day the U.S. B-29 Superfortress dropped the atomic bomb on Hiroshima 70 years ago this summer, none knew the four-engine bomber better than Capt. Robert Lewis.

On Wednesday, two of his wartime flight log books, Hiroshima bombing plans, mission notes and other items are up for sale during an auction of World War II material being held at Bonhams in Manhattan. The pre-sale estimate for the flight logs is $150,000 to $200,000.

Lewis, a 27-year-old pilot from Ridgefield Park, New Jersey, logged a total of 36 flights aboard the Enola Gay, including the Aug. 6, 1945, bombing mission that changed the world. A meticulous record-keeper, Lewis' handwritten entry in his personal flight log for that historic day reads: "No#1 Atomic bomb a huge success."

The flight logs covering Lewis' service in the Army Air Forces from 1942-46 are among an extensive archive of his documents handed down to his son, Steven Lewis. The younger Lewis said his father recorded details of every flight he took, including the three dozen he made aboard the Enola Gay.

"He wrote down everything and he kept everything," said Steven Lewis, 57, of Hampton Township, New Jersey.

"The Enola Gay was the most significant aircraft of World War Two," said Larry Starr, collections manager at the American Airpower Museum in Farmingdale, New York. "Any records of that mission would be significant."

As commander of the Hiroshima mission, Col. Paul Tibbets was also the pilot of the Enola Gay, relegating the lower-ranked Lewis to co-pilot. The move made Tibbets a household name after his crew completed the world's first atomic bombing mission, which destroyed much of the Japanese city and killed tens of thousands of its citizens. But Tibbets only flew the Enola Gay a couple of times, while Lewis had piloted the aircraft 16 times during test flights leading up to the Hiroshima mission.

"People don't realize how many times he flew aboard the Enola Gay," Steven Lewis said.

Three days after the Hiroshima bombing, another U.S. B-29 dropped an atomic bomb on Nagasaki. Japan surrendered six days later, ending the war.

Robert Lewis died in Virginia in 1983, Tibbets in 2007 in Ohio. Enola Gay navigator Theodore "Dutch" Van Kirk, the last surviving crew member, died in Georgia in 2014.

The other Lewis items for auction include personal photographs from the war and his hand-drawn diagram of the Hiroshima bombing run showing the bomb blast's expected shock wave range and the evasive flight path the Enola's Gay would take after detonation. Steven Lewis said he's putting the WWII documents up for sale ahead of his plans to publish his father's manuscript of wartime experiences in a book at a later date.

Hundreds of other WWII artifacts are being auctioned at Bonhams, from American flags flown at Normandy at D-Day to Japanese military maps of Iwo Jima.