If a merger doesn't happen, the debt will not be the reason. It's not ideal but it won't be the deal breaker. I saw somewhere else that AA and DL have like $8B in cash on hand and UA has something crazy like $15B. Do they want to assume the debt? Will they if they believe getting a major foothold into JFK soon is critical to their strategic long range plan? I think they would. Time's ticking. Trump has less than 3 years left.

Also, after all the negative press of the Fed government blocking a merger only to see a major airline go out of business, I don't think there would be much political pushback should a new merger be announced soon. Especially with JB not having made a profit in like 7 years, they can paint a picture where JB would follow Spirit's path, and no one wants that on their hands.