DENVER (AP) -- Indigo Partners LLC is going ahead with plans to buy Frontier Airlines, even though it failed to reach an agreement with the carrier's flight attendants' union.

The Phoenix-based firm agreed at the end of September to purchase Frontier from parent company Republic Airways Holdings on the condition it could successfully negotiate agreements with the pilots and flight attendants.

Indigo Partners said Friday it reached a tentative labor deal with pilots. In a statement late Wednesday, the firm said that agreement has not been reached with the Association of Flight Attendants, but it will waive that condition.

The deal, which is now based on equity and business conditions, is expected to close later this month pending regulatory approval.

"We are pleased about the progress we have made to resolve major issues and move this acquisition toward closing. We look forward to completing the action and continuing to extend Frontier's reach and service as a leading nationwide, ultra low-cost air carrier," said William Franke, managing partner at Indigo Partners.

Frontier Airlines said details will be discussed at a board meeting on Thursday.