Observed from the ground, the total solar eclipse happening on August 21, when the Moon completely blocks your view of the Sun, will be visible for up to 160 seconds. It will be a fleeting glimpse of a rare phenomenon, which is why NASA plans to chase the Moon's shadow using a pair of jets.
The planes NASA will be flying are modified versions of the WB-57F that first took to the skies way back in 1953 as bomber and reconnaissance aircraft. Both planes have been heavily upgraded with modern avionics, however, as well as a pair of telescopes on the nosecone of each that's capable of capturing photos, video, and thermal images of the eclipse, and of the planet Mercury, which will be more visible while the skies above the planes are considerably darker.
The total solar eclipse provides a rare opportunity for NASA to study the Sun's atmosphere, particularly its faint corona, which is somehow heated to millions of degrees while the actual surface of the star measures in at just a few thousand. The eclipse might not instantly reveal what causes this weird temperature difference, but the footage and photos captured will give NASA a chance to better understand what is going on out there.
Even with a top speed of well over 966km/h, the WB-57F jets won't spend hours basking in the Moon's shadow. Depending on where you are in the United States (and thanks to the curvature of the Earth) the Moon's shadow will be racing across the surface of our planet at speeds of over 3,862km/h. So NASA has calculated that each of its jets, which will be taking off from NASA's Johnson Space Center in Houston, will spend roughly three and a half minutes capturing images and footage before the shadow leaves them in the dust.