Frontier and Spirit Airlines will once again try to merge, only months after the Biden administration won a key antitrust court battle to block an attempt by JetBlue to buy Spirit. A combination of the two ultra-low-cost carriers would produce the country’s fifth largest airline,

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

The Denver-based low-cost carrier said its combination with the Dania Beach, Florida-based Spirit would create a stronger low-cost carrier and benefit “from the very significant synergies Frontier expects to achieve by combining the airlines’ operations.”