WASHINGTON — Millions of observers will watch next week’s American solar eclipse from the ground. But a few lucky NASA flight crews will get a much closer view.

When a total solar eclipse crosses North America on Monday, April 8, an estimated 31 million people will be in its path — watching. Many more are likely to travel for the event, which will be visible across large swathes of the US and Mexico.

All the best planning in the world can be scuppered by weather, however, as anyone who remembers the August 1999 eclipse in the UK will tell you, when clouds blotted out the show.

So, if you want to make sure you see a total solar eclipse, which only falls over a given location once every 375 years on average, what’s the best way to do it?

Take to the skies and fly above the clouds, of course.

That’s what four NASA pilots will be doing, together flying two of the agency’s specialized WB-57 planes off the coast of Mexico.

Here, following the path of totality — or total darkness — from southwest to northeast, they will remain in the shadow cast as the moon crosses the sun for seven minutes, compared to just four minutes available on the ground, studying the eclipse with numerous instruments as they do so at an altitude of 50,000ft (15km).

“It’s extremely exciting,” said NASA pilot Tony Casey, a sensor equipment operator (SEO) on one of the two aircraft. “I am stoked. I’m so excited to be able to fly this mission. I’m looking forward to just the experience of being there in this moment and the shadow overtaking you.”

Casey will be the second crewman in one of the two WB-57 planes, responsible for operating the aircraft’s instruments to study the eclipse.

Inside the nose of the plane, a camera and telescope system driven by Casey will be used to take images of the Sun in infrared and visible light, helping to study its atmosphere — its corona — as it dances around the Moon, and also looking for a dust ring and asteroids that might be visible near the Sun.

The planes “have this system that mounts onto the nose of the aircraft that allows you to put a telescope in there,” said Amir Caspi at the Southwest Research Institute in Colorado, a solar physicist who runs the experiment Casey will be operating. Similar experiments were conducted in 2017 when a previous total solar eclipse crossed the US.

About two hours before the eclipse, the two planes will take off from Ellington Field near NASA’s Johnson Space Center in Houston, Texas and travel down to Mexico. At the time of the eclipse each aircraft will be “about five or six miles apart”, said Casey, and traveling at 460mph (740 km/h).

That’s some way short of the speed of the eclipse shadow itself, which will move at about 1,600mph (2,500 km/h), but enough to give the planes a longer amount of time in totality than would be possible on the ground as they race along with the shadow.

“Obviously we can’t keep up with it,” says Casey. “So we want to be in the spot looking in the correct location and then, as soon as it’s totally obscured, we’ll follow that path all the way back to US airspace.”

The eclipse will be off to the right-hand side of the planes as they tear through the sky. Casey will be operating the camera as they do so, zooming in to different locations on the Sun while talking to the team on the ground.

“The field of view only covers a third of the Sun,” he said, so he’ll move the camera between each side of the star to get a total view during the eclipse and hone in on any features of interest such as an “interesting flare”, he added.

While operating the equipment is paramount, Casey hopes he may have time to actually glimpse the eclipse with his own eyes too. “We’ve got to verify that totality has been achieved before use this very expensive scientific camera and instrument,” he said. “But aside from a quick glance I will probably will be keeping my eye on the screen to make sure the instrument is not drifting.”

Being so high will give a view unmatched on the ground because of the thinner atmosphere. “It should be much crisper because you’re above the haze,” said Casey. That will also give scientific returns that cannot be matched on the ground. “The whole reason the sky is blue is because of [light] scattering in the atmosphere,” he says. “So you’re getting above a whole lot of that.”

The WB-57s are particularly suited to studying eclipses because of their long range — about 2,500 miles (4,000km) — and the large amount of time they can spend in the air, about six and a half hours. But they’re not just used for eclipses, with NASA also using the planes for other research or photography missions such as observing rocket launches.

In November 2022, Casey flew in one of the planes and photographed NASA’s Artemis I mission to the Moon, the inaugural launch of its huge new Space Launch System (SLS) rocket, and also photographed the first launch of SpaceX’s giant Starship rocket in April 2023.

That gives Casey probably one of the most impressive jobs around, but he keeps himself very firmly grounded. “I am a guy from a very small town in Northwest Alabama,” he says. “Somehow I have stumbled my way into this position where I fly in this extremely unique aircraft at the edge of the atmosphere and see rocket launches and now the eclipse. I’m just trying to do my best in the position that I’m put in. — BBC