TUCSON, Ariz. -- To the passing motorist, it's a giant parking lot packed with planes.

Military types call Davis-Monthan Air Force Base a "regeneration center" because all branches of the U.S. armed services send aircraft here for resting or retooling.

To aviators, including Capt. Chuck Osborn, a retired Delta Airlines pilot who served in the Air Force, this 2,600-acre, open-air warehouse is the Boneyard. He gives one-hour bus tours here for tourists, many of whom are gear heads.

Security is tight so you can't get off the bus to touch or board any of the more than 4,400 planes. But you will see the sleek flying machine Tom Cruise piloted in "Top Gun," the aircraft former U.S. Sen. John Glenn used to set a distance record and the H-1 Iroquois Huey helicopter, the angel of the Vietnam War.

Overhead, you may see a few A-10 Thunderbolts taking flight. Unofficially nicknamed the Warthog, this plane destroyed more than 1,000 Iraqi armored tanks and vehicles during Operation Desert Storm in the early 1990s. Like its namesake, it is prickly, mean and good in the mud.

"Before Desert Storm, they were considering taking that aircraft out of the inventory," Capt. Osborn said, but now the Warthog is likely to continue flying through 2024. "The main works of the cannon is behind the cockpit. It has a 30 mm Gatling gun on it."

Arizona's arid, desert climate and its soil, packed with clay, makes it ideal for supporting heavy aircraft, eliminating the need to build enclosed hangars. When a plane arrives, its fuel is drained at the "flush farm." To prevent internal rusting of the engine, 10/10 oil is circulated through the fuel system and the excess drained. Then, the plane is washed and taken to a long shed where armament, radios, instruments and ejection seats are removed and stored in a large brick building.

Finally, to protect it from the relentless Arizona sun, an aircraft is sprayed with a white liquid plastic that reflects heat away from the plane. The plastic keeps cockpit temperatures within 15 to 20 degrees of the outside air temperature. The bottoms of planes are left open to prevent moisture from building up inside.

"When they pull the aircraft out, they can see how the protective coating stood up to the weather in Tucson," Capt. Osborn said.

To understand aircraft designations, you need a basic knowledge of aviation's alphabet: A means attack, B for bomber, C for cargo, F for fighter, K for tankers, O for observation, S for anti-submarine patrol, T for trainer and Y for research. Concentration helps, too, because the tour covers a long Celebrity Row of planes.

Of the 700 civilians employed here, 600 are permanent while another 100 are hired to modify the wings of planes to update and extend the life of aircraft.

Aside from camera-toting tourists, the Boneyard sometimes attracts U.S. allies shopping for aircraft bargains.

There are used F-14s and F-16s, multi-role aircraft that can serve as air-to-air fighters or to deliver ordinance to the ground.

"Morocco and Italy were eager to have some used F-16s. Should one of our friendly foreign governments around the world want them, they can be refurbished and sold to a friendly ally of the U.S. government," Capt. Osborn said.

There's the OV-1 Mohawk, which the Army flew over Vietnam to study enemy lines, take pictures and fly over battlefields.

The Lockheed S-3 Viking was a carrier-based, anti-submarine aircraft used at the end of the Vietnam conflict and in Operation Desert Storm.

Military personnel were delighted to see the C-1 Trader because it carried mail and groceries.

Navy fliers loved the Grumman F-14D Tomcat, which is capable of Mach 2 plus, meaning it can fly faster than twice the speed of sound -- or a maximum speed of 1,544 mph.

"Tom Cruise flew this in 'Top Gun,' " Capt. Osborn said, but the plane was high maintenance because of the variable geometry of the swing wing, which allowed the pilot to select the correct wing configuration based on the plane's speed.

The Navy took it out earlier than it had anticipated and replaced it with an F/A 18 Hornet, which performed its fight or attack tasks more economically, Capt. Osborn said.

Among the Boneyard helicopters are the H-3 Sea King, used before and during the Vietnam War as a carrier-based helicopter that can do anti-submarine patrol. It also picked up astronauts who splashed down in the ocean after successful space missions.

There's the MH-53 E Super Stallion, a helicopter that flies presidents to Andrews Air Force Base and Camp David. But it also sweeps harbors mined with bombs.

The tour shows the enduring value of smart design. Air Force pilots still take off in aircraft that were designed more than 50 years ago, including the C-130 Hercules, the B-52 bomber and the F-15 fighters.

The B-52 first flew in 1952 and may still be here in 2050, thanks to a progressive maintenance program. Of course, the weapons have changed and the cockpits have been updated.

Developed in the 1950s and made by Lockheed in Marietta, Ga., the C-130 served ably in Vietnam and Afghanistan, and recently transported relief supplies to Haiti's earthquake victims.

"It can get in and out of shorter runways than the bigger cargo jets," Capt. Osborn said.

There's the F-8 Crusader, the first, carrier-based aircraft that could exceed 1,000 miles per hour. Built for the U.S. Navy by Vought in Dallas, Texas, this was the plane John Glenn used to set a cross-country speed record on July 16, 1957, when he was a Marine Corps major.

The Eurocopter EC-135 is a plane that served as a flying command post during the Cold War, when America feared its foes would lob a bomb onto a U.S. Air Force base.

"If Air Force base communications got knocked out, we had the flying command post. We had one or more constantly in the air. They had a general Air Force officer on board. He had the capability of communicating with the White House if there was a need for a retaliatory strike," Capt. Osborn said.

The LC-130 Hercules, which has retractable skis and can land on snow or ice, has been used by Navy pilots and the National Science Foundation.

Now, "The New York National Guard, out of Schenectady, N.Y., is flying those aircraft up in Greenland and in Antarctica. That's a fairly new mission for them in the last eight years," Capt. Osborn said.

Winner of the cuteness award is the T-37 Tweet.

"It's such a small airplane, they called it a little bird and sometimes referred to it as a Tweety bird. It was designed in the mid-1950s and came into the Air Force as the primary jet trainer for pilots. It had two jet engines and was fully acrobatic. Today, they have replaced it with a Texan 2, built by Beechcraft," he said.

Air Force pilots train for six months on the T-37 Tweet, then graduate to the T-38 Talon, the first trainer that flew faster than the speed of sound, Capt. Osborn said. The T-38 Talon has been overhauled with new instruments and still flies.

"Each one of the astronauts is assigned a T-38 as personal transportation. That makes it worth being an astronaut."

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