CHICAGO -- Saying they will not let the airline fail, union leaders at United Airlines have agreed to let the struggling company make huge cuts in labor costs. But is it enough?

The unions say they're ready to agree to $5 billion in cuts over five years, which includes savings from management, but the airline had said that it had been looking at $9 billion over six years to help avoid bankruptcy.

United has said it needs major concessions to secure a government loan guarantee.

The unions say their wage-cut and cost-savings proposal will allow the carrier to become $2 billion to $3 billion more profitable.

At least one industry analyst said he's not sure the rank and file is being sufficiently generous.

"The management said they needed the full amount of cost cutting," said Ray Neidl, an airline analyst at Blaylock and Partners. "I'm a little doubtful that there's room for much maneuvering."

A coalition of United unions delivered the proposal to United Airlines Chairman Glenn Tilton Wednesday evening.

Details of their proposal have not been released.

The five unions represent pilots, flight attendants, mechanics, baggage and ramp workers and flight dispatchers.

United's employees own 55 percent of the stock in UAL Corp.

Tilton has not announced how much he wants in cuts, but his predecessor wanted $1.5 billion a year in labor givebacks.

The machinists union had said that United was seeking $450 million in pay and benefit cuts from machinists.

Officials with the International Association of Machinists and Aerospace Workers said United was asking them to take 10 percent pay cuts and forego raises negotiated earlier this year for 2003 and 2004.