That would be true if they had to buy the planes. They don’t. Most of Spirit’s fleet is leased. And while Jetblue's fleet is the opposite, they have leased aircraft and actively lease aircraft.I don't think they have the cash to do that. Would have to get major injection of cash from a PE firm, and that takes time since they would need to have a shareholder vote on it as it would dilute the value of the shares.
Lessors would rather have JetBlue Airways operating those aircraft than a distressed carrier, so it’s largely a lease assumption and renegotiation exercise.
There are costs, but not "raise a pile of equity first" level costs. More of a "pick the best frames, assume/renegotiate the leases, replace the interior, align maintenance, and paint them" deal. Which is far FAR cheaper than new planes.
How much cheaper? If done properly, as a best case scenario hey could easily refit more than 20 Spirit planes to Jetblue's standard for the cost of one new plane.
Finally, this is a bit of futureproofing. There’s effectively a 10 year backlog on new A320 family aircraft. This is one of the few ways JetBlue Airways could add capacity without waiting until the 2030s.