AMNA NAWAZ: Twenty-five years ago, Hillary Clinton was the junior senator for the state of New York.

This week, she's reflecting on what's been lost and what she's learned in the generation since.

In her new essay for "The Atlantic" entitled "What the Aftermath of 9/11 Taught Me," the former secretary of state looks back at how leaders handled public health, national security, and transparency after the attacks, writing in part -- quote -- "There are many important lessons worth learning from 9/11.

This is one of them.

Government should be about producing results for people.

Our leaders need to level with people, tell them the truth, and follow through with actual results that make a difference in their lives."

Secretary Clinton joins me now.

Secretary, welcome back to the "News Hour."

Thank you for joining us.

HILLARY CLINTON, Former U.S.

Secretary of State: Thank you for having me, Amna.

AMNA NAWAZ: I do want to dig more deeply into this piece that you wrote for "The Atlantic."

But, on this day, I want to begin with your own memories of that day, because you were in D.C.

when the attacks unfolded.

You made it back to New York very quickly the next day on a special FEMA flight.

What do you remember about that moment in history?

What stays with you all these years later?

HILLARY CLINTON: Well, I have so many memories, but let me just highlight two of them.

Obviously, on the day of the attack, I was in Washington on my way to my Senate office.

I was going to attend a hearing that featured Laura Bush testifying about the Bush administration's proposals for education.

And so when the first plane hit, we were incredulous.

We couldn't understand how a plane could have literally run into an incredibly tall building in the middle of New York City, and began to reach out for information.

And then, of course, when the second plane hit, it became abundantly clear to everyone that this was not an accident.

And we spent the day trying to gather as much information as possible, trying to understand what the continuing threats were, because, as you remember, there was a third plane that went down in the fields of Pennsylvania after a plane had hit the Pentagon.

But it was thought that the plane that crashed in Pennsylvania was heading toward the Capitol itself.

So there was a lot of confusion and scrambling.

I watched every bit of footage that I could about what was actually happening in the city that I was then honored to represent, talking to people in all levels of government.

And then the next day, when Senator Schumer and I were, I think, the only civilian plane in the sky on the way from Washington to New York, we landed at LaGuardia.

We boarded a helicopter.

We asked the helicopter to fly us over Ground Zero.

And it is so indelibly just in my mind what I saw, because it was like looking at Dante's Inferno, looking at the twisted metal, looking at the burning fires, looking at the firefighters, the construction workers, others frantically continuing to try to carefully dig through all of that wreckage, with the hope that maybe somebody was still alive.

And then, when we landed, we met up with then-Governor Pataki and Mayor Giuliani and went toward the site itself on the ground.

And it was like seeing a curtain of darkness because of all of the particulates and the debris that was in the air, and you could smell it and you could taste it.

And I just left that experience not only incredibly moved and worried and fearful and angry and every other emotion you could imagine, but I left that first day worrying about the air, because I knew how it tasted and smelled and felt to me.

So that became an issue that I was particularly focused on in the days and weeks to come.

AMNA NAWAZ: And you write in this essay about knowing about those toxins in the air as early as August of 2003.

You note there was an EPA inspector general report that found White House officials had instructed the agency to reassure New Yorkers that the air was safe, despite the presence of some deadly toxins.

You said at a press conference afterwards, someone at the White House had to call someone.

Someone at the White House White House had to call or send an e-mail and tell the EPA, don't tell the truth.

You said: "I want to know who that is."

Did you ever find that out?

Will we ever find that out?

HILLARY CLINTON: I did not, and I don't know if we will.

I write that it was almost the most -- angriest moment in my public life that I had, because, for two years, we had been seeking answers.

We had been pushing our federal government to give us information.

And you referenced the desire on the part of our government to get Wall Street open, to get businesses up and going.

And I totally understand that.

I mean, obviously, we were devastated economically, as well as physically and loss of life.

But I think there could have and should have been better ways to send the messages, so that people would have been alerted that, no, it is not safe, wear a mask.

If you have asthma, if you have any respiratory problems at all, probably stay away.

We should have had a concerted effort by the city, state, and federal government to clean all of the buildings far better than they were, and on a repeating basis, because the searching on the pile was continuing, and there was a lot of construction equipment to move away huge steel beams, and that would release more debris and toxins into the air.

So one of the lessons I hope we have learned, but perhaps need to be reminded of, is, number one, level with people.

Try to find ways to meet more than one goal at a time, keep people safe, keep their lungs safe, but also try to let those people who are properly attired, who can manage to go back to work to do that on a staggered basis.

AMNA NAWAZ: You know, I should mention, Secretary Clinton, we had former Governor George Pataki on the show last night.

He was speaking with my colleague Geoff Bennett, and he was talking about his 9/11-related diagnosis of a restrictive airway disease.

He was diagnosed just in the last five years.

You were down there with him.

I have to ask, have you had any similar symptoms or are you worried you could develop them?

HILLARY CLINTON: Well, I heard about Governor Pataki.

And I obviously am very concerned for him, but I think he is kind of like the canary in the mine, in a sense that we know more and more people will be diagnosed.

I have not been, and I know many people who have, people who 10, 15, 20 years later, like the governor, are being told that probably this can be related in some way to your exposure on 9/11 and the weeks and months to follow.

So we're not through this.

And my hope is that, because of the information that is coming out, the 170,000 pages of additional information that advocates from a group called Health Watch were able to get from the city government now, that we take a hard look at what more needs to be done to reach out to people who might have problems in the future, to screen them and help provide the health care that they need right now.

Because I'm afraid that we're going to hear more stories like Governor Pataki's.

AMNA NAWAZ: I'd like to ask you about President Trump and what we heard from him and his remarks at the Pentagon to commemorate the 25th anniversary of these attacks.

He made the link to the war in Iran today.

He said, we're saluting those who served in the war in terror, and then he went on to say Iran will never have a nuclear weapon.

I wonder what you make of that linkage and the way the president made it.

HILLARY CLINTON: Well, I think he's looking for any explanation he can provide as to why he launched this war in Iran without fully understanding some of the consequences, like the closing of the Strait of Hormuz and the explosion in oil and gas prices that were precipitated because the strait was closed and tankers are not getting through.

Look, Iran has sponsored terrorism for many years, and we have seen the results, not just in the Middle East, but around the world, of attacks that Iran has either directly or indirectly supported.

So there is always ground to criticize and condemn Iran for their involvement in terrorism and the proxies that they support around the world who do their bidding.

But I don't see the connection between the current action in Iran and what happened on 9/11.

AMNA NAWAZ: Before I let you go, I want to ask.

As the nation is reflecting on this moment in history, for all the horror and the chaos of that day, there was this moment of unity we saw coming out of the attacks.

And I wonder what you think would happen in this nation today, divided as we are, if there was a similar-style attack.

How would our leaders respond?

How would our country respond?

HILLARY CLINTON: Well, I'm confident the American people would respond as we always do.

We would be reaching out to help.

There would be people running toward danger to help those who are at risk.

What I would hope is that, if it were to happen right now, that our current government would act out of a sense of generosity and inclusivity and reaching out to every American, not just the ones who support them, but every one of us would be part of the America that would be -- they would be concerned about.

So I hope nothing like that happens ever again in our country.

It was such a painful, terrible experience for the entire nation, and particularly for those who lost loved ones.

It was just a really terrible, terrible assault on our nation.

But we rose to it.

We were more unified than we have been in a long time.

So, we need to have a government that's as good in responding to disaster as the American people ourselves are.

AMNA NAWAZ: That is former Secretary of State Hillary Clinton joining us tonight.

Secretary Clinton, thank you for your time.

It's a pleasure to speak with you.

HILLARY CLINTON: Thank you.

Good to speak with you.