Northwest Airlines has extended the deadline for regional partner Pinnacle Airlines to pay another $21.7 million in aircraft sublease security deposits to April 15, as the sides continue to negotiate the terms of “their future business relationship.” In September Northwest requested that Pinnacle pay the additional funds by March 1, but the Memphis-based regional has refused.

Relations have become strained between Northwest and both its regional affiliates since the bankrupt major airline began making overtures for contract concessions last year, cut their fleets and sent requests for proposals to other airlines to perform Northwest Airlink flying. Pinnacle lost 15 of 139 Bombardier CRJs to Northwest’s cuts, resulting in an 11-percent reduction in ASMs. Mesaba has lost 12 of its 35 BAe Avro RJs and, according to Northwest’s plans, will completely exit Avro flying by the end of this year. Northwest has also cut 11 Saab 340s from Mesaba’s fleet and plans to remove another three this month. Northwest also halted Bombardier CRJ deliveries to Mesaba, leaving it with just two of a planned fleet of 15.

Meanwhile, Northwest has agreed to pay $2 million for the operating certificate of defunct low-fare CRJ operator FLYi, allowing it to accelerate preparations for the establishment of a wholly owned regional subsidiary. Last month Northwest reached a tentative agreement with its pilots to open a regional unit specifically to fly jets certified to carry between 51 and 76 seats.