It was my first glimpse of the valley. The photos, taken with a shaky telephoto through scratched Plexiglas, were not clear; but they showed two squarish white objects that looked like the tops of carved limestone pillars, opening into an area of low vegetation that was square in shape. The feature was on a brushy floodplain in the upper end of the valley. Everyone crowded around the laptop, squinting, pointing, and talking excitedly, trying to make sense of the pixilated images that were so tantalizingly ambiguous—they could be pillars, but then again they could be trash dropped from a plane or even the tops of two dead tree stumps.

I pleaded to accompany the third and final flight over T1, despite the logistical issues it posed. There was no room in the plane, but after some discussion, Chuck Gross agreed that he might be able to clear out a tiny space for me to crouch in. He warned me it would be mighty uncomfortable over six to seven hours of flying time.

On May 4, we arrived at the airport as the sun was just rising above the curve of the ocean, the plane throwing an Edward Hopper shadow across the tarmac. The soldiers guarding the plane greeted us sleepily. Now that I was about to be a passenger I looked at the plane more attentively, and I did not like what I saw.

“What’s with that oil streak?” I asked Chuck.

“Don’t worry about that,” he said. “I’m topping it off every day. In one flight it won’t lose enough to make a difference.”

As I crawled on board, my dismay deepened. The interior of the Cessna, once a rich velvetized fabric in burgundy, was now worn, greasy, and faded; much of the inside appeared to be held together with duct tape. It smelled of Eau de Old Car. Parts of the plane had been sealed with acrylic caulk, now peeling out in strings. As I tried to maneuver around the giant lidar box into the micro-space provided, I bumped my elbow into a panel, which fell off.

“No worries, that always happens,” said Gross, reseating it with a blow from his fist.

I marveled that a plane as unsafe and decrepit as this one looked would be used to carry a million-dollar scientific instrument. Chuck firmly disagreed. “No, sir,” he said. “This plane’s a perfect platform for the job.” He assured me the 337 Skymaster was a “classic,” and a “great little aircraft.” Unlike a King Air or a Piper Navajo, he said, this craft was ideal, with a fuel efficiency that would allow us to spend “six hours on station.” Even though it was forty years old, it was “totally dependable.”

“What if we go down?”

“Wow,” said Chuck, “what a question! First thing, I’d look for a clearing to set it down in. It’s uncharted territory: You’re out there on your own, out in the middle of nowhere, no two-way coms.” He shook his head—unthinkable.

Despite my worry, I had a lot of confidence in Chuck because I had learned of his feats of flying; at the age of eighteen, he had soloed across the Atlantic, one of the youngest pilots to do so. I hoped the aircraft’s deficiencies were mainly cosmetic. I told myself a world-class pilot like Chuck would never fly a plane that wasn’t safe.

I jammed myself behind the lidar box: no seat, my knees in my mouth. Juan Carlos was right in front of me. He was concerned about how I would fare; I sensed he was worried I might get airsick and vomit down the back of his neck. He asked if I’d had anything to eat or drink that morning. I said no. He casually mentioned how grueling it was out there, flying low and slow over the jungle for six hours straight, banking steeply turn after turn, tossed around by thermals, sometimes dodging vultures. The A/C on the plane was broken, he said; we would be sealed in a metal tube flying in full sun. The plane had no bathroom. If you had to go, you went in your pants. I tried to assure him I would be an exemplary passenger.

Elkins gave me a GoPro video camera and a still camera with a telephoto lens and asked me to take more pictures of the mysterious white pillars and anything else of interest I spied down below.

Chuck Gross climbed into the pilot’s seat and began running down the checklist, while Juan Carlos jacked his laptop into the lidar box. He showed me the flight plan he had programmed on his computer screen, dozens of parallel lines crisscrossing the valley, designed to maximize coverage while minimizing flight time. In addition to being a lidar engineer, Juan Carlos was also a licensed pilot, enabling him to work seamlessly with Chuck.

We took off from Roatán and were soon winging over the glittering Bay of Honduras, the mainland looming up ahead. It was a gorgeous day, the sky dotted with fluffy white cumulus. Far ahead, where the blue mountains of Mosquitia rose up, we could see the cloud cover was sparse and high. As we flew inland, the settlements along the coast gave way to scattered hamlets and agricultural fields alongside slow brown rivers. The land mounted into forested foothills, where hundreds of ragged patches of clear-cutting came into view. Plumes of smoke rose from the jungle in every direction.

The logging holes eventually disappeared and we were flying about four thousand feet over unbroken, precipitous forest. Chuck maneuvered his way through the mountains as we approached T1. An hour out of Roatán, Juan Carlos pointed out the rim of the valley in the distance, a wall of green mountains with a sharp notch in them. Chuck eased the plane to a lower altitude and we cleared the rim at a thousand feet, which gave a tremendous view of the landscape. As the land dropped away beyond the rim, I was struck by the valley’s picturesque topography, the ring of mountains embracing a gentle, rolling landscape divided by two rivers. It really did look like a tropical Shangri-la.