Buckling under roughly $13 billion in debt, broadcast and print media giant Tribune sought protection from creditors with the filing of a Chapter 11 petition in a Delaware bankruptcy court on Monday. Based in Chicago, the Tribune Company owns the Chicago Tribune, the Los Angeles Times, and ten other newspaper properties scattered across the nation’s largest media markets. The company also owns 23 broadcast television stations, cable TV super station WGN, major league baseball’s Chicago Cubs, and Wrigley Field. Monday’s bankruptcy filing came less than a year after Chicago real estate tycoon Samuel Zell took Tribune private while adding $8.2 billion in new loans to the company’s existing debt load of $5 billion. Sources close to the company indicate that steep losses in Tribune’s print advertising revenues combined with the ongoing credit market crunch have placed Tribune in a position of not being able potentially to meet its upcoming debt covenants. Last month, Tribune reported third quarter losses of $124 million that stand in contrast to profits of $84 million posted during the third quarter of 2007. In addition to debts of $12.9 billion, Tribune’s bankruptcy petition lists $7.6 billion in assets. While boasting of “significant progress internally on transitioning Tribune into an entrepreneurial company that pursues innovation and stronger ways of serving our customers,” Zell acknowledged that, “factors beyond our control have created a perfect storm . . . that makes it extremely difficult to support our debt.” Zell stressed, however, that Tribune has enough cash on hand to operate its TV, newspaper and other assets during the Chapter 11 process.