The original U-2, developed in complete secrecy, took its first flight in August 1955.

Sixty-four years later, the Dragon Lady is still prowling the skies, but with a whole new set of controls and sensors.

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Since the mid-1950s, the US Air Force's U-2 Dragon Lady has been cruising the upper reaches of the atmosphere, snooping almost totally unnoticed.

While the mission is pretty much the same, the aircraft doing it are much different.

"The 'U' in U-2 stands for 'utility,' so a lot of people are like, 'OK, 1955, what are we doing in 2019, when we're flying F-35s and F-22s ... why are we flying the U-2 that was built in 1955?'" Maj. Travis "Lefty" Patterson, a U-2 pilot, said during an event hosted by the Air Force in May at the Intrepid Sea, Air, and Space Museum in New York City.

"Much like the Corvette, which has been around for a long time, there's been a lot of different versions of [the U-2]," Patterson said. "The U-2s that we fly now, they were all built in about the mid-'80s."

"The jets are actually pretty new," U-2 pilot Maj. Matt "Top" Nauman said at the event. "They're a lot newer than people anticipate, even though it's been flying for more than 60 years."

'It's just the name is old'

The last of the original batch of U-2A aircraft at the US Air Force Museum. US Air Force

The U-2A was the first to fly, when its massive wings accidentally turned a high-speed taxi test into a flight test in August 1955. It was followed by the U-2C, which had a new engine.

To overcome range limitations, the Air Force and the CIA outfitted U-2As and U-2Cs for aerial refueling; they became U-2Es and U-2Fs, according to The Drive.

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In the early 1960s, the desire for more range led to the development of carrier-capable variants. Landing on a carrier proved challenging though, and several U-2As were modified with stronger landing gear, an arresting hook, and wing spoilers to decrease lift. These became the U-2G and U-2H.

The U-2R, which first flew in 1967, was 40% larger than the original and had wing pods to carry more sensors and fuel, allowing for high-altitude stand-off surveillance. (The U-2R was tested for carrier operations, but a naval variant of the U-2 never entered service.)

A U-2 on the flight deck of the aircraft carrier USS America. US Navy

The last U-2R arrived in 1989, and since 1994 the US has spent $1.7 billion to modernize the airframe and sensors. After the GE F118-101 engine was added in the late 1990s, all U-2s were redesignated as U-2S, the current variant.

Between 2002 and 2007, Lockheed upgraded the U-2's 1960s-era cockpit avionics with the Reconnaissance Avionics Maintainability Program, or RAMP, replacing dials and gauges with multifunction displays, an up-front control and display unit, and a secondary flight-display system, according to Military & Aerospace Electronics.

The new displays were more user-friendly and offered a better view of the ground to the pilot, who previously had to look into a large tube in the center of the cockpit. RAMP also made the radio controls easier to reach.

The most recent cockpit upgrades were completed in 2013, Lockheed said last year. Other modifications have been floated in the years since, aimed at keeping the U-2's sensors robust and resilient.

The Air Force currently has about 30 of the single-seat U-2 for missions and four of the two-seat TU-2, which is used for training, based at Beale Air Force Base.

Lt. Col. Lars Hoffman in a new Block 20 U-2S, with a redesigned cockpit, at Osan Air Base in South Korea, June 20, 2006. US Air Force/Staff Sgt Andrea Knudson

Each U-2 gets a full overhaul every 4,800 flight hours, or about every six to eight years. Because the airframe doesn't spend a lot of time under high stress, the current lifespan for a U-2 is into the 2040s and 2050s.

The Air Force still has a few of the U-2s built the late 1960s, but those have been converted, Patterson said.

"Everything's modern — just the airframe itself came out in '69. The engine, the cockpit's all new," he added. "But most of the aircraft that we have, they're all built in the mid-'80s, about the same time as the B-2 stealth bomber."

Read more: The Air Force is changing the way it recruits U-2 pilots — here's what it's like to fly the US's oldest working spy plane

The newer models, Patterson said, "are about 40% larger [and] significantly more powerful than the original lot of U-2s that you saw when Gary Powers was flying over the Soviet Union, when the Cuban missile crisis is occurring, so it's a totally different aircraft — modern glass cockpit, so we have screens. We have extremely advanced sensors."

"So it's not an old aircraft. It's just the name is old."

'Mr. Potato Head'

A U-2, with a satellite communications system on its back and antennas on its belly, over California, March 23, 2016. US Air Force/Staff Sgt. Robert M. Trujillo

By the mid-1960s, US officials were already talking about retiring the U-2, but it survived and has outlasted other reconnaissance aircraft, like the SR-71, which were more expensive to operate.

Unlike satellites, a U-2 can be sent to peer at an area of interest on relatively short notice. It also has advantages over unmanned aerial vehicles, like the RQ-4 Global Hawk, Patterson said.

"When you think about some of the capabilities that our adversaries are able to put into the field pretty quickly and pretty cheaply — GPS jamming and things like that — it definitely pays dividends to have a human being that's able to react real-time to developing situations."

A human pilot is also better with unfamiliar surroundings, he said. "I can deploy anywhere in the world because I don't need to program a new airfield. I can just take my airplane and land it ... and I can take off within hours."

U-2 pilot Maj. Ryan before a sortie in Southwest Asia, February 2, 2017. Air Force/Senior Airman Tyler Woodward

Nauman and Patterson both touted the U-2s versatility.

"The ability for this platform to adapt to the newest imaging technology is a key piece of" its continued relevance, Nauman said. "With the size, weight, and power ... we're talking about 5,000 pounds of payload."

That's 2,000 pounds more than the RQ-4's payload. The U-2's ceiling is also above 70,000 feet — more than 10,000 feet above the ceiling of the RQ-4.

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The U-2 can also test technology at high altitudes before it makes the leap to space. "The ability to actually get the most modern technology before it gets to space is kind of what makes us relevant," Nauman said.

Other technology and payloads can be swapped onto the U-2, helping "to keep the cost down, accelerate development timelines, get these things in the air, and make sure that we run through all the issues," Patterson said. "Then we can proliferate those [things] throughout the Air Force."

US Air Force Senior Airman Charlie Lorenzo loads test film into a camera in preparation for a U-2 mission in Southwest Asia, April 17, 2008. Air Force photo/Senior Airman Levi Riendeau

"The U-2's almost like Mr. Potato Head," Patterson said, describing its adaptability.

"So you can take a pod off here and a nose off here and put a new thing on pretty quickly, just because it's got big wings, it's got a big engine, so we've got a lot of size, weight, and power advantage over a lot of other high-altitude aircraft."

The most well-known U-2 sensor is probably its optical bar camera.

"It's effectively a giant wet-film camera. ... It fits up in the belly of the aircraft. It's got about 10,500 feet of film" that used to be made by Kodak, Patterson said. "In about eight hours, we can take off and we can map the entire state of California."

The U-2 no longer does overflights of unfriendly territory, Nauman said. But its suite of cameras and sensors allow it to pick up details whether it's looking straight down or looking hundreds of miles into the distance.

An airman reviews film from a U-2 mission. The Wall Street Journal

"Let's say we don't want to fly that camera in the belly. We can take the nose off, and we can put a giant radar on the nose," Patterson said.

"With a big radar up in there in the front," you can gather imagery out to the horizon, he added. "If you think about how far you can see if you're parked off somebody's coast with a 300-mile looking glass, it's pretty phenomenal."

The U-2 can also be outfitted with what Patterson described as "like a big digital camera" with a lens "about the size of a pizza platter." With multiple spectral capabilities, "it's imaging across different pieces of the light spectrum at any given time, so you can actually pull specific data that these intel analysts need to actually identify" the composition of particular materials.

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Signals payloads also allow the U-2 to pick up different radars and other communications.

"We have a number of antennas all across the aircraft that we're able to just pick up what other people are doing," Patterson said. "We bring all that on board the aircraft, and we pipe it over a data link to a satellite and then down to the ground somewhere else in the world."

"While we're sitting by ourselves over a weird part of the world doing that [intelligence, surveillance, and reconnaissance] mission, all the information we're collecting is going back down to multiple teams around the globe."