Spirit Airlines rejected a $400 million merger proposal from Frontier this week, saying the offer was financially inadequate and came too late. Spirit Airlines declined an opportunity to merge with rival low-cost airline Frontier on Wednesday.

Rather than accept Frontier’s offer, Spirit said it will stick to its current plan to emerge from Chapter 11 bankruptcy.

Spirit, which filed for bankruptcy protection last year, says it has rejected the new Frontier overture but would be open to a higher offer.