The bankruptcy of American Airlines means cutbacks at South Florida’s dominant air carrier, which has been a source of growth during dark times for the economy and the tourism industry.

Unable to cut costs enough to fend off creditors, American and its parent company, AMR Corp., filed for Chapter 11 protection Tuesday morning while it tries to lower its debt and reorganize its business. American is one of the five largest private employers in Miami-Dade County, with about 9,000 workers.

The filing triggered a flurry of paperwork sure to raise anxiety across South Florida’s large network of American employees and vendors. Foreign and domestic suppliers were instructed how to get on a list to collect money from American, and AMR said it plans to begin labor talks under the auspices of a federal bankruptcy court in New York.

Miami-Dade County is listed as being owed $29 million, making it the second largest creditor outside of AMR’s lenders. Hewlett-Packard is the largest at $30 million.

American had been building the new North Terminal at Miami International Airport but the county took over the project amid financial turmoil and construction delays.

American executives emphasized passengers should not notice a difference, with reservations, frequent-flyer miles, and routes remaining untouched for the foreseeable future. AMR has about $4 billion cash in its coffers, which executives said should make the restructuring easier on operations.

“The No. 1 message we’re trying to get out to customers is you can book with us with confidence,’’ said Craig Kreeger, head of customer service for American.

Investors were rattled by the news, including the abrupt exit of CEO Gerard Arpey. AMR stock plunged almost 90 percent Tuesday morning, from about $1.60 a share to 26 cents.

Since 2000, American has only turned a year-end profit once: in 2007, just a global recession was beginning. Higher fuel costs this year made the financial picture much worse. American said it paid $3.15 per gallon in the first nine months of 2011, up 40 percent from 2010. This year’s $884 million loss between January and September amounts to about $3 million in losses a day. Last year, the AMR was losing just over $1 million a day.

The Dallas-based airline is responsible for about 70 percent of the traffic at Miami International Airport, which is one of American’s five hubs across the country. That status meant something of a windfall for Miami during the recession, with American adding flights out of MIA amid cutbacks by competitors across the country. American funnels most of its Latin American connections through MIA, and Latin American routes contributed about 20 percent of American’s $22 billion in revenue last year, according to regulatory filings.

American’s expansion throughout the downturn led to worry that the airline was too optimistic, since it was the only one of the major established carriers not to file for bankruptcy after the 2001 terrorist attacks. Kreeger said Miami will remain a hub after American’s bankruptcy, and that the growth in key markets didn’t contribute “significantly” to the company’s financial woes.

“While we have been growing in those [hubs], we have not been growing significantly as an airline,’’ Kreeger said. “That strategy remains a key building block for the successful strategy of our company. We look forward to continuing to focus on our key markets...Miami remains a key cornerstone in a large part because it is a key gateway for Latin America.’’

Kreeger also noted that cost reductions are likley through the American system, but the company has not offered any details. “We anticipate some trimming to become more optimal,’’ he said.

The nation’s third-largest airline said Arpey was replaced by company president Thomas W. Horton.

AMR Corp. has continued to lose money while other U.S. airlines returned to profitability in the last two years.

Horton said the board of directors unanimously decided to file for bankruptcy after meeting Monday in New York and again by conference call on Monday night.

American said it would operate normally while it reorganizes in bankruptcy.

The Associated Press contributed to this report.