Miami's tourism industry is threatened by politicians who run the airport for the benefit of cronies - not millions of passengers.

Miami International Airport, rated among America's worst for passengers, is being used by Miami-Dade politicians as a billion-dollar piggy bank to enrich their friends and campaign contributors.

They manipulate rules so favored firms get airport deals. They delay for years other airport services, such as luggage carts, because companies haven't cut in the right people. They dictate everything from where rental car companies line up along the counter to how many firms will clean airport bathrooms.

Miami-Dade Commissioner Pedro Reboredo once put it succinctly: "The main problem is us - politicians - involved in the process."

A Miami Herald investigation proves that's true. From thousands of MIA files and hundreds of interviews emerges a portrait of an airport where political deal-making is more important than developing an inviting hub for travelers. The result: an airport that is threatening the region's economy and viability as a hemispheric commercial center.

Key findings:

Virtually all major deals at MIA go to companies that give political contributions and employ lobbyists who are key fund-raisers and advisors for county politicians. Outsiders, including American corporate giants such as Disney, can't get in.

Major companies seeking work at MIA frequently are forced to give a piece of their deals to politicians' allies who have no experience in airport work.

Example: Jorge de Cardenas, a lobbyist and campaign strategist with no background in retail sales, drew regular checks from his cut of the airport's duty-free deal - while serving time in prison for his role in a Miami bribery scheme.

Minority hiring programs are sometimes exploited. In one case, a politically active multimillionaire with a waterfront home and a 54-foot yacht was slipped into a lucrative deal as a "disadvantaged businessman."

Companies with the right connections get MIA's millions without ever going through a bid process. Firms offering long-distance phone cards and baggage wrap at the airport have operated for years on no-bid "test permits" - despite evidence they don't offer travelers the best deal. Travelers at MIA pay $6 to get a medium-size bag wrapped. In San Francisco, the charge is $3.

Politicians shape contract specifications to help favorites. Some companies are given so many extra points for being locally based that outsiders who offer far better prices can't get MIA's business.

In the case of a parking management contract, that meant a company partnering with a local businessman tied to several county commissioners got more points than a national company that offered a price 44 percent better.

Reforms have done virtually nothing.

A "cone of silence" that was supposed to reduce lobbyists' influence after projects are advertised has failed. Much of the lobbyists' efforts go into shaping contract specifications - an activity that happens before the cone of silence descends.

In many cities, aviation experts run the airport. At MIA, politicians - encircled by a phalanx of lobbyists - micromanage an operation that rings up hundreds of millions of dollars in yearly sales.

The result of their manipulations: an airport that is threatening the area's tourism industry, which creates 300,000 jobs, and the community's role as a hemispheric commercial center.