Last year, an American disappeared while traveling alone in a small plane in West Africa, heading to a new job as an anti-poaching pilot in a national park. Investigators think he hit a mountain but the location of his Cessna 172 remains a mystery after a search stymied by limited resources, patchy help from local authorities and forested, mountainous terrain.

Bill Fitzpatrick's last contact with aviation authorities was on the night of June 22 when he calmly gave his position and altitude to a control tower during a nighttime approach to coastal Cameroon. Then, nothing. Both man and plane vanished.

"Jungle will swallow up a small airplane," said Ray Kapteyn, aviation program manager in Cameroon for SIL, an organization based in Dallas, Texas that translates the Bible and took part in aerial searches for Fitzpatrick's plane. SIL also searched for a Cessna 182 originating in Germany that disappeared in roughly the same area in August, possibly after crashing at night into the Gulf of Guinea.

Kapteyn noted that radar coverage in the area is poor, but he said: "It is a little bit unusual that there were two of them in such a short time."

The fate of vanished aircraft, rare in an increasingly mapped and technologically connected world, is the stuff of intrigue, fueling theories about the cause and speculation about the last moments of those aboard. American aviator Amelia Earhart disappeared over the Pacific in 1937, and the hunt is still on for Malaysia Airlines Flight 370 in the Indian Ocean after it went missing with 239 people aboard in 2014.

This weekend, media quoted Chilean mountaineers as saying they found the wreckage of a plane in the Andes that went missing 54 years ago. It had crashed, killing 24 people, including eight members of a professional soccer team.

Fitzpatrick, 59, was flying from Kano, Nigeria to Douala, Cameroon and his final destination was to be Odzala-Kokoua National Park in Congo, which is managed by African Parks, a nonprofit group based in Johannesburg. The Central African park, which consists mostly of rainforest, hosts gorilla researchers and tourists who join expeditions tracking the great apes.

The job of the former Peace Corps volunteer would have been to scan the park's many clearings for elephant carcasses from his cockpit and alert rangers who could intercept poachers escaping with ivory tusks.

"Everything is in limbo," Fitzpatrick's brother, Ken, said in a telephone interview from his home in Ridgefield, Connecticut. The missing pilot's wife, Paula, and their three children live in Chelan, Washington.

Bill Fitzpatrick learned to fly when he was 17, and once took primatologist Jane Goodall for a spin over San Francisco Bay, his brother said. Bill Fitzpatrick previously worked as a ranger and pilot at North Cascades National Park in Washington state, Arctic National Park in Alaska and elsewhere.

There was no mayday signal on the night of his disappearance, suggesting he crashed into a mountain without time to react, and that weather or a fuel shortage was not the cause. No signal was detected from the plane's emergency transmitter, which can be activated on impact or by the pilot.

African Parks has discounted the possibility that the aircraft may have been shot down by any military forces in the area.

Cameroonian troops canceled a ground search, citing a lack of fuel, said David Zeller, manager of Odzala park at the time.

Zeller said Cameroonian authorities let him listen to recordings of the radio transmission between Fitzpatrick and air traffic controllers, but he was not allowed to record or transcribe them. He believes the plane crashed in an area of the Bakossi mountain range with heavy cloud cover.

On behalf of African Parks, anti-poaching consultant Gauthier Selva also visited Cameroon. Some villagers tried to cash in, offering to rent him a truck with a driver for two or three days for $1,000, Selva said. He also talked by telephone with a man who asked for money to reveal the crash site, but did not send a photo to prove his information was correct.

The American's takeoff from Nigeria was delayed because he had to make cash withdrawals to pay for fuel, according to a witness. Despite the increased risk of flying at night in an unfamiliar area, he apparently decided to leave around 6 p.m. because his Nigerian flying permit was expiring that day, African Parks said.

The U.S. State Department says it is monitoring the case and providing consular assistance to Fitzpatrick's family, which wants Washington to deploy surveillance equipment and other resources to search for the plane.

Fitzpatrick's brother said he informed the FBI of purchases of items including a laptop and a camera made on Bill Fitzpatrick's PayPal account after his disappearance. Zeller said those transactions could indicate the pilot was either scammed on his journey through West Africa, or somebody found the plane wreckage in Cameroon and stole financial details from his laptop.

Fitzpatrick built an aircraft hangar in Odzala before going to pick up the Cessna. Torsten Bohm, a German who was researching hyenas in the park, smoked cigars and chatted with Fitzpatrick.

"Bill is such a wonderful person," Bohm said in a July email to colleagues. "I especially liked his 'everything is possible' attitude and he showed me that sometimes some things should not be taken so serious."