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CARL AZUZ, CNN STUDENT NEWS ANCHOR: Know your national parks! You're going to learn a lot about them over the next 5 days as CNN Student News celebrates National Park Week. Hello, everyone. Welcome to today's show. I'm Carl Azuz.

First Up: Polish Funeral

AZUZ: We begin today in Poland, where President Lech Kaczynski and his wife have been laid to rest. They were killed in a plane crash last week in Russia. More than 90 other passengers on the flight, including many Polish officials, died as well. Yesterday, Kaczynski's twin brother led mourners at the funeral. Tens of thousands of people gathered on the streets in Poland as the president and first lady's coffins were brought to the service. Many stayed outside the cathedral in a large square where the ceremony was shown on giant TVs. Yesterday's service concluded a national week of mourning in Poland. Some officials estimated that more than a million people took part in events that paid tribute to President Kaczynski. Russia's president, Dmitry Medvedev, attended yesterday's funeral. Other world leaders, including President Obama had planned to be there, but they weren't able to make it.

Volcano Close Up

AZUZ: That was because of huge clouds of ash coming out of a volcano in Iceland. You see some of the images over my shoulder here. The volcano started erupting last month; it got worse last week. That is when officials started getting concerned about the ash, especially about the effect that it could have on planes. One expert explains the reason for their concern.

MARY SCHIAVO, FORMER INSPECTOR GENERAL, U.S. DEPARTMENT OF TRANSPORTATION: When it gets into the jet engines and the jet engine inlets, literally, it remelts this material, this ash material, and it forms a glass-like substance on the jet engine vanes, and the parts and it can clog them and it will stop them.

AZUZ: Having an engine stop in midflight, not something you want. That is why so many flights have been canceled and why so many world leaders weren't able to attend the funeral in Poland. The impact of this on the aviation industry has been massive; bigger than you might think. Some officials are saying it's actually worse than the time right after the 9/11 terrorist attacks in 2001. And there's an economic impact here, too. According to experts, airlines have been losing at least $200 million a day. That means as of yesterday, they'd wracked up about a billion dollars in losses. There is some possible good news, though, especially for all of the travelers who've been stranded. Officials ran a few dozen test flights yesterday and said the skies over a lot of Europe might be safe for air travel, although they couldn't make any guarantees. Meantime, Gary Tuchman has some incredible pictures to show you. He took a helicopter to the volcano where all this ash is coming from. Check out what he found.

(BEGIN VIDEO)

GARY TUCHMAN, CNN NATIONAL CORRESPONDENT, ATLANTA: This was the first day visibility was good enough to see up close the Iceland volcano erupting. So, we flew aboard a helicopter to get as close as the pilot dared. He dared to get a lot closer than we imagined, only several hundred feet away from a display that looked like it was from another world. Boulders shooting out of the crater, lightning bolts in the smoke that towered hundreds of feet high.

Looking at this volcano erupting this close up is both awe-inspiring and frightening. It's been quiet since the 1820s. This volcano stopped erupting in 1823; it had been doing so for about two years. It's hard to imagine the economic catastrophe if it lasted that long now.

This part of the mountain range is where the eruption began last month. Now, it's mostly quiet with just pockets of smoke. But here, the eruptions are huge, dramatic, and show no signs of weakening. There is another nearby volcano called Katla which hasn't erupted in almost 90 years, and historically erupts around every 50 years. It's feared it could be far more devastating than this one.

HREGGWIDAR NORDDRAHL, UNIVERSITY OF ICELAND: Magma might find its way from this volcano into Katla. What happens then, I don't know.

TUCHMAN: So, is it possible the magma from this volcano could cause Katla to erupt?

NORDDRAHL: It might cause some activity, yes.

TUCHMAN: We found it hard to believe we could fly right next to this incredibly powerful display of mother nature, while whole countries are closing down their airports because of it. And there is absolutely no way of knowing how long it will last. Gary Tuchman, CNN, Hvolsvollur, Iceland.

(END VIDEO)

Jobless Benefits

AZUZ: In the United States, lawmakers have signed off on help for some people who are collecting unemployment benefits. That's the money that the government gives to people who don't have a job. Benefits ran out for more than 200,000 people earlier this month. But late last week, the Senate passed an extension so they could keep getting money, and President Obama signed it into law. This bill was scheduled to be voted on earlier in the month, but there was some debate over how it would be paid for; that led to the delay. People affected by the extension will get back pay -- that means they'll get some of the money they missed -- to cover the weeks when their benefits had expired.

This Day in History

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April 19, 1775 - The American Revolution begins with the battles of Lexington and Concord.

April 19, 1995 - A bomb destroys most of the Alfred P. Murrah Federal Building in Oklahoma City, Oklahoma, killing 168 people.

April 19, 2005 - Cardinal Joseph Ratzinger is elected to be the 265th pope; chooses the name of Pope Benedict XVI.

Oklahoma City Memorial

AZUZ: One of those historic moments you just saw is bringing people to downtown Oklahoma City today. It's the 15th anniversary of a tragic bombing that took place there. The Alfred P. Murrah building was eventually torn down, and this memorial was built on the site, along with a museum that's dedicated both to teaching people about the tragedy and educating visitors about the impact of violence in general. Beyond the nearly 170 people killed in the Oklahoma City attack, more than 500 others were injured. Today's ceremonies, which include memorial services and a day of community service, pay tribute to all of those victims.

Is This Legit?

TOMEKA JONES, CNN STUDENT NEWS: Is this legit? Yellowstone was the first national park in the U.S. This is true! Yellowstone was the first of the country's 392 national parks.

National Park Week

AZUZ: We said it at the beginning of today's show: It is National Park Week. And in honor of that, the National Park Service is waiving entrance fees to all 392 parks. They're totally free. What we're going to do is spotlight just a few of those parks starting with the very first one: Yellowstone. It was founded as a national park in 1872, more than 40 years before the National Park Service was even created. Yellowstone, if you've ever been there, you know it is massive. It covers nearly 3,500 square miles and takes up parts of Wyoming, Montana and Idaho. Home to all sorts of wildlife. It might be most famous for its geysers, including Old Faithful, which erupts pretty regularly, every 30 to 120 minutes.

Thunder Fireworks

AZUZ: Well, it's not as old as Yellowstone, but this Kentucky fireworks show knows how to bring the thunder. It's the Thunder Over Louisville, the country's largest annual fireworks show, and it's a blast. The Thunder is part of the opening ceremonies for the Kentucky Derby Festival. The horse race isn't for another couple weeks yet, but there are a lot of events leading up to it, including this illuminating display. Officials estimate that 700,000 people came out for the 21st annual Thunder. The show was delayed by about 15 minutes because of a computer glitch, but after a quick reboot, things went off without a hitch.

FIRST Robotics

AZUZ: Some fireworks happening here in Atlanta this weekend, too. But the electrifying display we're talking about now was indoors, and it was in the heat of competition. The FIRST Robotics Competition. FIRST meaning "For Inspiration and Recognition of Science and Technology." The organization's goal: to inspire young people to be leaders in science and technology. And competitions like this are part of the way it does that. You've heard us talk on our show about how women are under-represented in those fields. We stopped by FIRST and talked with some of the female participants about their thoughts on that.

UNIDENTIFIED FEMALE, FIRST COMPETITOR #1: Science and technology is important at our school just because it proves that we can do one more thing that everyone else can, that all the guys can.

UNIDENTIFIED FEMALE, FIRST COMPETITOR #2: It's important just to show that girls can do anything that boys can do and get our name out there as well.

UNIDENTIFIED FEMALE, FIRST COMPETITOR #1: It also gives you the chance to really prove yourself, stand up for the rest of women. Kind of be an example, showing what we can do and that there should be more women in science.

UNIDENTIFIED FEMALE, FIRST COMPETITOR #3: In order to solve what's going on in the present and the future, we need to really focus in on science and technology and really take advantage of it.

Downloadable Maps Promo

AZUZ: From Europe to Yellowstone, Oklahoma to Atlanta, we've covered a lot of ground today. Our downloadable maps can help students pinpoint exactly where we've been. Head to our home page, CNNStudentNews.com, scroll all the way down, and look on the left-hand side. That is where you'll find these free geographic guides.

Before We Go

AZUZ: Things you say to your dog: sit, stay, shake hands, roll over, play dead, get ripped! A California gym owner is letting dogs tread on her treadmills! Even the fittest canines aren't really built for barbells. They'd probably rather chew on the bench than press from it. But when you can bring your best friend along on your best workouts, he'll finally know where you go, why you come home smelling so bad...

Goodbye

AZUZ: ...And why you get so dog tired. I'm Carl Azuz. That shapes up all of today's headlines on CNN Student News.