. Cargo planes operate under less stringent safety rules than passenger planes, and cargo pilots are allowed to fly up to 40 percent more hours a year. Yet they work in a pressure-cooker environment to deliver goods on time, often flying in icy, hazardous weather.

One pilot, so tired that he had previously fallen asleep at the controls, begged for someone to join him on a flight in June 2005. No help came, and that morning the 27-year-old died when his plane crashed into a Colorado mountain.

His Utah cargo company had been fined seven times in five years for a string of safety violations, yet it continued to fly despite its spotty record and failure to pay most of the fines. The FAA revoked its license, but only after the deadly 2005 crash.

In Ohio, a cargo company with a history of deaths praised its pilots for finishing their flights with scarce fuel.

. In nearly a quarter of fatal crashes, mechanical problems were not fixed before cargo pilots took off, a safety breakdown that would be unacceptable in passenger planes.

One veteran cargo pilot pleaded with the FAA for help, writing of "crews pushed to fly exhausted . . . cargo doors opening, engines flaming out."

Not long after, slipshod maintenance caused one of that company's planes to crash in a California auto salvage yard, killing three.

. The FAA allows cargo companies to continue operating despite blatant maintenance lapses and histories of crashes.

For years, the FAA knew an Albany, N.Y., cargo company had four planes that were not certified to fly in icing conditions, but never enforced its own rules -- until one of the planes crashed in icing in New Hampshire in 2000, killing the pilot, 39.

In a pattern repeated across the country, FAA inspectors unearth problems, some of them alarming, and cargo companies promise repairs. The planes are soon back in the air, only to encounter more mechanical failings. The industry's most troubled operators shut down only after death tolls rise or finances dwindle.

. Two turboprops that are among the most popular in the industry, the Cessna 208B and Mitsubishi MU-2, account for one-fourth of all fatal crashes.

The FAA twice denied requests from Mitsubishi to boost pilot training programs, only to see the MU-2 involved in repeated crashes. The Cessna continues to fly despite urgent concerns, spelled out in the government's own memos, about the plane's handling in icing.