Some trekking operators, which act as brokers and take a percentage of rescue fees from helicopter companies, make more money through evacuations than they do charging for hikes. The typical profit margin for each hiker heading to Everest might be just a few hundred dollars. Participating in the scam could net operators thousands of dollars in kickbacks.

The investigation last year by Traveller Assist found evidence of fraud by four hospitals and 13 helicopter, charter and rescue companies. The separate investigation by Nepal’s government identified most of those same companies. A few dozen more trekking companies are thought to be involved.

“To say this is a complex problem is an understatement,” said Danny Kaine, head of assistance at Traveller Assist. “Fraud and corruption in the helicopter rescue industry in Nepal are so ingrained in some companies. It has become an accepted way of doing business.”

Insurance companies initially struggled to track the fraud, though it has been occurring since at least the early 2010s. But over the last few years, the number of insurance claims from Nepal shot up dramatically.

Alarmed at the increase, travel insurance companies created internal blacklists of Nepali helicopter companies and hospitals, posted advisories warning trekkers of the scam and raised premiums.

Traveller Assist found that about 1,600 helicopter rescues had occurred in Nepal from January to August 2018, out of which 35 percent were considered fraudulent, costing insurers some $4 million in losses.

In September, Nepal’s government introduced a new monitoring program that required companies to submit bills to the department of tourism to ensure that they were genuine.