On the 50th anniversary of its first flight, a history of the DC-3 illustrates its importance to aviation.

NASA's Cassini probe explores Saturn's icy rings and moons, capturing ring-moon interactions and revealing ingredients for life on the moon Enceladus.

Jupiter's gravitational force made it a wrecking ball as it barreled through the early solar system, but it also helped shape life on Earth as it brought comets laden with water and possibly the asteroid that put an end to the dinosaurs.

The rocky planets Mercury, Venus, Earth and Mars all have similar origins, but only one supports life.

Consistently stunning documentaries transport viewers to far-flung locations ranging from the torrid African plains to the chilly splendors of icy Antarctica. The show's primary focus is on animals and ecosystems around the world. A comic book based on the show, meant to be used an as educational tool for kids, was briefly distributed to museums and schools at no cost in the mid-2000s.

"American Experience" combines dramatic re-enactments with commentary by historians and authors to present an absorbing look at the personalities, events and resources that have had a profound impact on the shaping of America's past and present. Many of the program's documentaries have received major honors in the broadcasting community, including Emmy, Peabodys and duPont-Columbia University awards.

This award-winning series presents compelling untold stories and covers a wide array of provocative subjects. "Explorer" aired for 25 years -- the longest-running documentary series in cable TV history -- before being relaunched in 2015 after a five-year hiatus. Each monthly episode of the new "Explorer" takes a similar deep dive inside a story from the pages of a recent National Geographic magazine issue, taking viewers not only to the most remote corners of the globe but also to the furthest reaches of the mind and deepest crevices of history -- on urgent missions of discovery.

"Frontline" offers an unflinching and compelling look at complex, vital and often-controversial subjects. Each broadcast consists of a long-form news documentary. Topics run the gamut -- from Bernie Madoff's intricate fraud and prisoner abuse at Abu Ghraib, to AIDs, racial issues and Wal-Mart's effect on the U.S. economy.