NEW YORK (CNN/Money) - UAL Corp.'s United Airlines, which filed for bankruptcy-court protection a week ago, has told its unions it needs $2.4 billion in annual labor concessions by mid-February if its lenders will provide it with the needed financing.

The Association of Flight Attendants' Web site told its members about the new $2.4 billion annual cost cut target, which is about 150 percent above the almost $1 billion in annual savings that United had negotiated before the bankruptcy filing.

The union's site said that management told union leadership last week it needed the deeper cuts in order to get the next round of financing it needs to support operations in bankruptcy, known as debtor-in-possession financing. The airline has only gotten $800 million of the $1.5 billion in DIP financing it says it needs.

"Bankruptcy is an expensive endeavor, with legal and bankruptcy consultants' fees totaling in the hundreds of millions of dollars when all is said and done," warned the AFA site. "The most important condition to us is that the lenders are requiring the airline to reduce its costs by about $2.4 billion annually. Those cost reductions must be secured by mid-February. Thus, things will happen very fast."

The union said that it would seek to negotiate to minimize the cuts as much as possible, but it warned members that the company would likely be able to go the bankruptcy court judge and have that level of cuts imposed on membership.

"Not negotiating leaves all of the control in the hands of management," said the site. "We want to keep as much control over this impossible situation as we can. In the end, you will get a chance to vote on any agreement we reach."

The Web site for the unit of the International Association of Machinists that represents about 13,000 mechanics and plane cleaners at United also warned membership that management is seeking an immediate 13 percent wage cut. The membership of that IAM unit rejected a request for a 7 percent wage cut that would have saved about $700 million over 5-1/2 years shortly before the carrier filed for bankruptcy court protections.

The United proposal also calls for eliminating a number of job security provisions from the mechanics' contract, including a requirement that heavy maintenance of planes be done within the United States and provisions that prohibits United from selling or leasing its three major maintenance facilities.

"United indicated that their proposal was a starting point for further discussions," said the IAM District Lodge 141-M Web site. "District 141-M is now reviewing the term sheets with our financial and legal advisors. We also expect to discuss the proposed terms with the United Airlines Union Coalition. We have not agreed to any further discussions with United Airlines at this time."

The wage concession package negotiated by the airlines' unions disappeared with the rejection of the airline's request for $1.8 billion in federal loan guarantees, as well as the "no" vote by the mechanics. All the union packages were contingent on all the employee groups agreeing to the cuts, and the loan guarantees keeping the carrier out of bankruptcy. United therefore has continued to pay near industry-leading wages to its union employees and faces up to $22 million in daily losses while it tries to win new cost cuts.

An official with the Air Line Pilots Association said the union was "stunned" by the new cost cut demands from management. A spokesman said the union is looking at the company's proposal, and can't say whether it is willing to negotiate deeper cuts.

"We're still waiting for a full picture of what the plan is going to look like," John Hartz, spokesman for ALPA.

United spokesman Joe Hopkins wouldn't comment on the new proposed cuts. UAL CEO Glenn Tilton warned on the eve of the bankruptcy filing that deeper wage cuts would be needed at the airline, and that changes in work rules would also have to be agreed to by unions to improve productivity.

Analysts said Monday the new cuts are a step towards what the airline will need to survive, but even this level of cuts won't ensure the carrier's survival.

"That would certainly go a long way to helping the company," said Jim Corridore, airline equity analyst for Standard & Poor's. "Labor costs are the biggest bucket they can attack. The government might be more willing to help with this level of cuts. Even with DIP financing, they're going to face a liquidity problem. They could use those loan guarantees."

Corridore said he was somewhat surprised that the company went ahead and paid $70 million in retroactive pay owed to the IAM members at the airline last week, even as it was missing almost $1 billion in scheduled debt payments.

"I guess they want to keep that union from revolting," he said.

Ray Neidl, analyst with Blaylock & Partners, said that the company will face problems if it tries to force the cuts on the unions in bankruptcy court.

"If unions don't want to play ball, they could destroy your service levels and chase away customers," said Neidl. "You're also not sure you'll get the changes in the contract from the judge. You're much better off if everyone could get it together."

In other news, United announced it is moving ahead with plans to share passengers with another bankrupt carrier, US Airways. The so-called "code share" agreement allows the carriers to book their passenger on each other's flights. The agreement, announced earlier this year, takes effect Jan. 7, the companies announced Monday. Flights on United became available to those booking through US Air Sunday, and flights on US Air can be booked through United beginning Tuesday.

Shares of UAL (UAL: down $0.20 to $1.55, Research, Estimates) were down about 15 percent in Monday trading.