United Airlines, the bankrupt US carrier, is considering plans to cut an additional 6,000 jobs - 10 per cent of its workforce - and take another $655m out of annual operating costs, as part of a more radical overhaul of its business plan.

The airline needs aggressive changes after the Airline Transportation Stabilisation Board rejected its application for a $1.6bn federal loan guarantee at the end of June.

United is now dependent on the capital markets for financing to enable it to emerge from bankruptcy protection, where it has been since November 2002.

According to people familiar with the discussions, the airline is preparing a new plan that Glenn Tilton, chief executive, will take to United's board at the end of September.

In a bankruptcy filing two weeks ago, the company warned that deeper restructuring was imminent.

“The hard truth is that these proceedings have reached a critical crossroads at which poor decisions based on bygone paradigms cannot be afforded and tough ones can no longer be avoided,� it said.

Although the plan has not yet been finalised and remains the subject of further talks with its unions and the creditors committee, it is understood to include proposals to cut more than 6,000 jobs, phased in over time as part of productivity changes and further outsourcing.

The reductions would come on top of an already steep fall in its workforce, from 104,000 before September 11 2001 to 62,000 now.

United wants to save about $3bn in cash over the next four years by terminating its defined-benefit pension plans, but talks about alternatives to termination are continuing with its unions.

The airline, which has already cut more than $2.5bn from its annual cost structure, has identified another $655m in incremental savings through, for example, benchmarking its non-labour costs against industry best practice.

Management is also trying to avoid turning to private equity groups for financing to enable it to leave bankruptcy.

One person familiar with the plan said: “It is in the creditors' best interest that the plan is all debt-financed, so there is no dilution from private equity, so creditors will get more dollars for their claims. Airline management does not want to involve new equity.�

The airline has sought to improve its relationship with its creditors committee. A separate sub-committee of the creditors' committee has also been created this month to take a more hands-on role in the restructuring talks. It includes the airline pilots' union, the Pension Benefit Guaranty Corporation, Lufthansa and Stark, as advisers to the committee.

In the last two weeks United has set up working groups, which will include input from the committee, to assess the carrier's network, outsourcing, exit-financing and United Express, its regional operations.

One person involved in the talks said: “For the first time since they filed for bankruptcy, there is a willingness to co-operate with creditors.

“They don't want to get into a situation where the committee comes up with a competing plan.�

Last week, the airline reported net earnings of $6m for July, usually one of the most profitable months for the airline.

Jake Brace, finance director, noted: “The fact we were only able to deliver a modest net profit underscores the ongoing challenge of record high fuel prices exacerbated by a weak revenue environment.�