Reading deeper into this, they should make it another 12 months - basically they're relying on cash from GTF engine failures that are grounding a significant percentage of their fleet, but due to GAAP this can't be relied upon income, hence the required going concern notice. If these planes were in operation presumably they'd make enough money to keep the airline healthy-ish.
Spirit has other financial health issues of course, so it could easily implode anyway for other reasons, but this isn't it.
Side note: Eastman Kodak also just filed the same notice for related GAAP reasons.