Having flown on military aircraft in the past, I had an idea what to expect when I climbed aboard a World War II-era Boeing B-17 bomber, known as the Flying Fortress.

But I did not realize until arriving at Bolton Field June 28 that a B-17 cabin is not pressurized, that is it has open windows and, on the particular plane in which I rode, what amounted to a sunroof.

This was a different experience, as I could see the tarmac below the plane during takeoff through small openings in its floor.

As the plane accelerated for takeoff, the engine roar reminded me of the sound of the starting grid of the Indianapolis 500.

My opportunity to hitch a ride on the B-17 was possible because the Liberty Foundation, owners and operators of the plane, had invited the media on board in advance of a weekend event at Bolton Field Airport that offered rides in the B-17, as well as a Curtiss P-40E Warhawk fighter plane.

The nose of the B-17 on which I flew was emblazoned with a buxom woman and the cursive words, "Memphis Belle."

While not the original Memphis Belle, this B-17 was the same plane flown during filming of the 1990 movie of the same name, a fictional account of the Memphis Belle crew that completed 25 combat missions.

The last surviving member of the crew, radio operator Robert Hanson, died in 2005.

The original Memphis Belle was part of the 91st Bomb Squadron of the Eighth Air Force. Between Nov. 7, 1942, and May 17, 1943, the crew of Memphis Belle completed 25 successful bombing missions, mostly in France and Germany.

"A lot of (B-17s) did not even finish five missions," pilot Ray Fowler of the Liberty Foundation told the media prior to takeoff.

Capt. Robert Morgan named Memphis Belle after his girlfriend, who lived in Memphis, and even commissioned an artist from Esquire Magazine to render the curvy woman depicted on its nose, as well as many other World War II-era planes.

The Memphis Belle returned to the U.S. before the end of the war and was used for publicity and selling war bonds, but then fell into ruin while stored at a site in Memphis. In 2004, the National Museum of the United States Air Force took ownership of it. It is currently being restored at Wright-Patterson Air Force Base in Dayton for display in the museum.

About one in three of every B-17s in service during World War II was lost.

There were 12,732 B-17 planes produced from 1935 to 1945; 4,735 were lost in combat. Following World War II, B-17s were used in the Korean War, the 1948 War in Israel and even the Vietnam War.

Today, only 13 B-17s are airworthy and it is the mission of the Liberty Foundation to preserve such planes in operable condition.

The B-17 in which I flew was never used in combat and was sold as surplus to the National Metals Co. of Phoenix for $2,687, and then to Fast Way Air of Long Beach, Calif.

In the 1960s, the craft was used as a water bomber and then as a tanker until the late 1970s.

The Military Aircraft Restoration Corp., started by American businessman David Tallichet, next purchased the plane, restoring its tail gunner compartment, Sperry dorsal turret and other equipment recovered from a wreck.

The inside of the plane was sparse, but it was what I expected, with low overheads, metal seats and protruding beams. One unexpected sight were cables that raced back and forth overhead, moving as the pilot, far aft, pulled the levers that moved the rudder and other control surfaces.

It costs about $4,500 per flight hour to operate a B-17, a sum far greater than I would have guessed.

The Liberty Foundation spends more than $1.5 million annually to keep its two planes, the B-17 and the P-40E, airworthy and on tour so private citizens can be afforded the opportunity to ride in the aircraft and experience military history.