Spanish contractor Ferrovial's bidding team is thought to be planning cuts to BAA's £2.7bn expansion of Stansted airport.
The group's acquisition vehicle, Airport Development and Investment, has worked up an alternative plan that it has already presented to the Department for Transport and the Civil Aviation Authority.
Since Ferrovial's £10bn bid for BAA last week, speculation has been rife that BAA's 10-year, £9.5bn capital expenditure programme will be cut back to recuperate some of the contractor's debt.
In its offer document to BAA shareholders, Ferrovial said: "An alternative capital expenditure plan, already flagged to the CAA and the DfT, has been developed by ADI for Stansted. ADI believes this plan, together with its fresh approach to stakeholder consultation, will allow BAA to meet the needs of all stakeholders within the current framework. Overall, ADI believes its approach is strongly aligned with the interests of users."