Hillary Clinton wants to know what’s out there.

In March, Clinton — the presumptive nominee for the Democratic nomination for president — went on Jimmy Kimmel Live and said she’ll do her best to delve into government files surrounding possible UFO sightings.

“I would like us to go into those files and hopefully make as much of that public as possible. If there’s nothing there, let’s tell people there’s nothing there,” Clinton said on Kimmel’s show.

“If there is something there, unless it’s a threat to national security, I think we ought to share it with the public.”

Clinton isn’t alone in her curiosity about aliens on Earth.

According to one poll released in 2012 and conducted by the company Kelton Research, about 36 percent of the United States population believes in UFOs.

“This is not a fringe thing,” SETI Institute astronomer Seth Shostak told Mashable in an interview.

The Central Intelligence Agency has released a full database of public UFO files, yet the interest in a possible government conspiracy still hasn’t died down.

If Clinton is chosen as the nominee and eventually elected as president, she will join a list of presidents who also have thoughts about UFOs, and even their own sightings to share.

Harry Truman

One of the main incidents that sparked UFO fever in the United States happened during Harry Truman’s presidency in the 1940s.

In 1947, an object crashed near Roswell, New Mexico sparking years of UFO conspiracy theories that have persisted through today. After initial media reports classified the object found in Roswell as a “flying saucer,” the U.S. military claimed it was actually a weather balloon.

In fact, the piece of debris appears to have been part of a project called “Project Mogul” designed to spy on Soviet Union nuclear tests, according to the History Channel.

For his part, Truman joked about flying saucers with the media at least once, according to a transcript of a press conference from July 10, 1947.

When asked if he had seen any flying saucers by a reporter Truman said, “Only in the newspapers,” joking after a follow up, “did you ever hear of the moon hoax?”

Jimmy Carter

Former president Jimmy Carter has a very personal relationship with the controversy surrounding UFOs.

Carter has opened up about a UFO sighting he experienced while in Georgia, in 1969 before his presidency began.

“I was outside a school lunch room one night right before sundown. It was getting dark and we were getting ready to eat supper. And I and about 25 men were standing around and all of a sudden in the western sky we saw a strange light coming toward us, a round light,” Carter said on Larry King Live.

“It got closer and closer and right above the pine trees it stopped and then it began to change colors from blue, to red, to white. Then it stayed there for a while. We were all aghast. We didn’t know what it was. And then it just disappeared into the west. That was the end of it.”

"I have never thought and still don’t think it is possible for creatures from Mars to visit us."

Carter didn’t attribute the event to some kind of alien encounter, however.

“I have never thought and still don’t think it is possible for creatures from Mars to visit us and then come back home,” he added.

During his presidency, Carter also asked NASA to investigate UFOs, according to Leslie Kean, investigative journalist and author of the book UFOs: Generals, Pilots and Government Officials Go On the Record.

"Carter made a request through his science advisor Frank Press in 1977 asking NASA to look into UFOs, Even though the request came from the highest office in the land, NASA declined," Kean told Mashable via email.

"This shows that even presidents can not always get information about some topics."

Ronald Reagan

In 1974, Ronald Reagan may have seen a UFO, according to the book UFOs: Myths, Conspiracies, and Realities written by Army Col. John Alexander.

According to an account by pilot Bill Paynter, Reagan was flying in a plane with Paynter and others when they say a “big light flying a bit behind the plane.”

That light then accelerated to a high speed and flew off.

Paynter didn’t file a report, but, according to Alexander, the pilot and Reagan would talk about the UFO experience.

Alexander also said that Reagan discussed the UFO sighting with a reporter at the Wall Street Journal.

"We followed it for several minutes. It was a bright white light. We followed it to Bakersfield and all of a sudden, to our utter amazement, it went straight up into the heavens,” according to Alexander’s book.

Bill Clinton

Hillary Clinton’s husband and former president Bill Clinton, also spoke out about his thoughts regarding aliens and UFOs on Jimmy Kimmel Live in 2014.

Bill said that he looked into the truth about Area 51 when he was president and had “all the Roswell papers reviewed,” anticipating that the White House would get a lot of letters on the anniversary of the Roswell incident.

“First I had people go look at the records on Area 51 to make sure there was no alien down there,” Clinton said during the appearance.

“People thought that because everyone who works there has to stop about an hour away and put on special clothing and then drive in and out, and that’s because a lot of our stealth technology is made there. We know that now, but there are no aliens there.”

Bill Clinton is a space geek when it comes to science in general as well.

On that same appearance with Kimmel, Clinton waxed a little poetic about how there is, in fact, a good chance that life in some form exists out in the universe. Clinton said that there are plenty of planets outside of our solar system that could potentially support life.

“It makes it increasingly less likely that we’re alone,” Clinton said.

Barack Obama

President Barack Obama has commented on possible alien conspiracy theories a few times during his presidency and even during his campaign.

Most of Obama’s comments about possible UFOs or aliens tend to be on the joking side or are used as an attempt to pivot back to issues affecting people living on Earth now.

For instance, during a 2007 debate, presidential hopeful Dennis Kucinich was asked about a somewhat bizarre story involving his report of seeing a UFO.

When Obama was asked his thoughts pertaining to “life beyond Earth” on the heels of that story, he said “I don’t know and I don’t presume to know. What I know is there is life here on Earth and that we’re not attending to life here on Earth.”

In 2015, Obama also went on Jimmy Kimmel Live and joked about UFOs. But the president did get a little more serious about UFOs in an interview with Bill Simmons for GQ.

“People always ask me about Roswell and the aliens and UFOs, and it turns out the stuff going on that’s top secret isn’t nearly as exciting as you expect,” Obama said during the interview. “In this day and age, it’s not as top secret as you’d think.”

In 2013, during Obama’s presidency, the government also declassified more than 60 documents from the 1960s and 1970s about goings on at Area 51, according to Space.com.