The Lago de Cote Aerial Photograph, Costa Rica 1971

Costa Rica, 1971. The Instituto Costarricense de Electricidad was planning the Arenal hydroelectric reservoir. It needed maps to determine water levels for land acquisition. The job went to the Instituto Geográfico Nacional.

The survey aircraft was a twin engine Aero Commander 680F. Omar Arias was the pilot. Sergio Loaiza, an aerial photographer and cartographer, operated the camera. Juan Bravo and Francisco Reyes completed the crew of four. Under the fuselage hung a Zeiss RMK 15/23 mapping camera, donated by the German government.

September 4, 1971. A little after eight in the morning. The aircraft crossed Lago de Cote, a small crater lake near Arenal, at 10,000 feet. The camera fired on its own, one frame every 13 to 20 seconds, depending on the account. The crew noticed nothing unusual.

Frame 300 was different. Against the uniformly dark water sat what Richard F. Haines and Jacques Vallée would later describe as "a large three-dimensional disk, or shallow cone," above the lake and possibly partially submerged in it. It was in sharp focus and looked metallic. A fuzzy area marked its left side. Frames 299 and 301 show nothing at that spot.

Sergio Loaiza had no idea. Two or three years later, a colleague interpreting the photos called him over. "Look, what is this thing? It looks like a flying saucer."

Loaiza says he does not know how the Vílchez brothers got hold of the image. In 1979 Ricardo Vílchez sent it to Ground Saucer Watch in the United States, which judged it to have been made in good faith. On November 1, 1979, La Nación printed it with an arrow pointing at the object. The Tico Times later claimed the crew had been forbidden from discussing it publicly.

In the late 1980s Jacques Vallée brought the photo back from Costa Rica. With Richard F. Haines he examined the original negative, using enlargements at different contrasts and computer enhancement. Their 1989 paper in the Journal of Scientific Exploration concluded: "An unidentified, opaque, aerial object was captured on film." They found "no visible means of lift or propulsion" and no sign of double exposure or deliberate fabrication. If the object was at lake level, its maximum length would be 210 metres, or 683 feet. Haines answered the film flaw question plainly. "The image was smooth as glass so it set to rest that argument."

Some believe the photograph shows only the wake of a boat. On Metabunk, posters in a thread led by Mick West favoured a defect: a pressure mark from grit trapped in the film roll, an emulsion bubble, a reflection inside the lens. No shadow falls on the lake, though the sun was about 16 degrees up. Nobody on the ground reported seeing anything. The widely shared version turned out to be rotated compared with the archive images, and a popular "4K" copy shows signs of AI upscaling. The negative has never been examined under raking light.

Farmers had reported strange, artificial objects moving around the surface of the lake or just below it. The original negative remains in the Costa Rican national archive. On September 4, 2026, the 55th anniversary, The Cote Photo by Adam Pillon and Megan Woomer was released. In it Sergio Loaiza, now 83, speaks at length on camera for the first time, alongside Esteban Carranza and Leslie Kean.