Chicago ? United Airlines reached a tentative contract agreement Friday with its mechanics union, the last labor group to agree to long-term cuts in pay and benefits as part of the carrier’s drastic overhaul in bankruptcy.

Chief executive Glenn Tilton touted the completion of initial agreements with all unions as an “extraordinary” achievement for United.

But even if all the accords are ratified by union members, the airline faces a struggle to restructure and meet its lenders’ strict benchmarks amid an unprecedented slump in the industry, compounded recently by the war in Iraq and the SARS virus.

The agreement announced Friday calls for 13 percent wage reductions, new work rules and a 20 percent co-pay on health insurance over six years. The airline’s 12,000 mechanics and aircraft cleaners will vote on the agreement on April 29.

The contract would lower company costs by $349 million a year through 2008, or a total of $2.09 billion.

The airline indicated the deal would provide the last remaining portion of the $2.56 billion in annual labor savings it seeks to be more competitive.

Without an agreement, bankruptcy court hearings were set to begin Monday on United’s motion to void the mechanics’ contract May 1. If the mechanics fail to ratify it, United can still have its own wages and work rules imposed in bankruptcy court starting on that date.

“From the moment United Airlines declared bankruptcy on Dec. 9, a painful restructuring was inevitable,” said Scotty Ford, president of IAM District 141-M representing the mechanics. “Despite proposed changes to pay, benefits and working conditions, this agreement preserves the essential value of a job at United Airlines.”

Even though United could force through its own contract changes in bankruptcy court, the airline wants to reach consensual deals to avoid a recurrence of labor trouble, which could be fatal for its reorganization.