Wright-Patterson Air Force Base, Ohio - The historic, final toast of the Doolittle Raiders is expected to attract thousands of people and the Air Force's top brass today to the National Museum of the U.S. Air Force.

Three of the four surviving Raiders will gather from across the country at the museum to toast the memory of their fallen airmen who took part in the April 18, 1942, mission that bombed Japan just months after Pearl Harbor. The raid shocked and embarrassed Japanese military leaders and boosted American morale. Two months later the tide of the Pacific war turned with the U.S. victory over the Japanese at Midway.

"We know there's going to be a huge crowd, and I am absolutely certain that we're going to see thousands and thousands of people here," said John "Jack" Hudson, museum director and a retired Air Force lieutenant general. "This is the final event that they're going to do in any kind of public setting, and they had always envisioned their final event to be that toast."

Air Force Chief of Staff Gen. Mark Welsh, the service branch's top uniformed leader, and acting Secretary of the Air Force Eric Fanning, the top civilian leader, are scheduled to attend, Hudson said. Visitors from as far away as China and Europe will be at the event, said spokesman Rob Bardua.

The gathering will pay homage to the Raiders, who under the command of then Lt. Col. Jimmy Doolittle took off in 16 Army Air Force B-25 Mitchell bombers from the deck of the Navy's USS Hornet to bomb Japan. The mission was the first U.S. strike against the island nation since the Japanese Imperial Navy attacked American military bases at Pearl Harbor on Dec. 7, 1941.

Raiders expected to attend today are: Richard E. Cole, 98, a Dayton native living in Comfort, Texas; Edward J. Saylor, 93, of Puyallup, Wash., and David J. Thatcher, 92, of Missoula, Mont. Robert L. Hite, 93, of Nashville, Tenn., will not attend because of health reasons, officials said.

The final salute will mark the sixth time the Raiders gathered at the museum since 1965, and the first since April 18, 2012, when four airmen of the World War II bomber crews commemorated the 70th anniversary of their mission.

More than 150 volunteers will help at the event, which has been in planning and preparation for more than a year, said Teresa Montgomery, the museum's chief of special events.

"It takes a lot of intricate planning, from beginning to end," she said. "We have spreadsheets on top of spreadsheets to make sure this goes smoothly."

Today's events begin at 1:15 p.m. ET with a "grand arrival" of the Doolittle Raiders with crowds lining the long driveway to the museum.

A 2 p.m. memorial service is set for the museum's memorial park. Cole, Doolittle's co-pilot, is scheduled to speak to the crowd, officials said.

At 2:30 p.m., six B-25 bombers from across the nation will fly over the gathering.

The day's events will be capped at a 6 p.m. toast, which will be televised on the Pentagon Channel and live streamed on the museum's website: www.nationalmuseum.af.mil. Eighty silver goblets commemorate every Doolittle Raider. Each year, surviving Raiders hold a toast using the goblets to remember their fellow airmen. One by one, over the years the goblets of those who have died the previous year are turned upside down to mark the airmen's passing.

The toast is an invitation-only ceremony, but the other events are open to the public, Bardua said.

The museum theater will screen World War II-themed movies, such as "30 Seconds Over Tokyo," "Restorers: We Were All Volunteers" and "Honor Flight: The Last Mission." Author Stan Cohen will autograph his book "Destination Tokyo."