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.

Frontier Airlines is making another offer to merge with bankrupt Spirit Airlines, less than two years after a previous plan fell through.

Frontier Airlines is attempting for a second time to merge with the now bankrupt Spirit Airlines, which declared bankruptcy late last year as budget airlines struggle.

Spirit Airlines rejected Frontier Airlines' second attempt to merge the two companies on Wednesday and will continue with its plans to exit bankruptcy. Frontier made an offer in early January for Spirit stakeholders to acquire $400 million in new debt and obtain 19% of Frontier's stock.

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

Frontier said in a release that it has met with Spirit’s board and executives since it made its proposal this month.

Budget carrier Frontier Airlines announced on Wednesday that it has made another bid for fellow discount carrier Spirit Airlines, which is in bankruptcy, for an undisclosed sum.