CHICAGO (Reuters) - Oscar Munoz, the new chief executive at United Continental Holdings Inc (>> United Continental Holdings Inc), will be expected to persuade investors and employees that he can fix a complex business in an industry in which he has no experience. He's done it before.

When Munoz, 56, arrived at CSX Corp (>> CSX Corporation) in 2003, the Jacksonville, Florida-based railroad was struggling. CSX and Norfolk Southern had carved up Conrail, a large rail network in the U.S. Northeast, but CSX failed to consolidate Conrail's operations and was essentially running two networks, with the worst safety record among the major railroads and the worst operating ratio.

"We were the biggest excuse machine east of the Mississippi," said one current CSX manager who declined to be quoted by name. The company seemed ready to be "broken up, gobbled up or go bust," he said.

Munoz had held finance jobs at consumer products companies including Coca-Cola Enterprises (>> Coca-Cola Enterprises Inc), AT&T Corp [TATTC.UL] and Pepsico Inc (>> PepsiCo, Inc.) before joining CSX. But people familiar with his time there said he moved to reduce back office employees and shed some 2,200 miles of poorly performing tracks, port assets and other things the railroad did not need. He is largely credited for changes that made CSX an industry leader in safety and steadily improving financial performance, people familiar with his tenure said.

In 2004, Munoz took a seat on the board of Continental Airlines Inc, and stayed on when Continental merged with United Air Lines to become United Continental. Like CSX, United Continental has struggled to effectively integrate its operations. It suffered from data system crashes that disrupted service, and wrestled with disgruntled unions.

Munoz is succeeding Jeff Smisek, who abruptly departed after running United Continental since 2010.

"In the cut-throat airline business if you do the wrong thing customers go away and the wrong thing can be as simple as having a ticket price that is $10 higher," said Morningstar analyst Keith Schoonmaker. "So it will be interesting to see how Munoz adapts to that market." At CSX, he said, customers often only have two choices among railroads.

Munoz said Tuesday during a call with analysts he sees close parallels between the challenges of big railroads and big airlines. Both industries must manage complex technology, attend to customer service, contain costs, generate cash and return cash to shareholders. Safety is critical for both industries, he said.

"The airline industry has been closely watching, monitoring, exactly what the rail industry has done,” Munoz said.

(Reporting By Joe White, editing by Joe White and John Pickering)

By Nick Carey and Joseph White