WordNet records no synonym and no antonym for flame-out. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the failure of a jet engine caused by an interruption of the fuel supply or by faulty combustion
a complete or conspicuous failure
“the spectacular flame-out of the company's stock cost many people their life savings”
Synonyms, antonyms and the broader and narrower relations for flame-out come from Princeton University’s WordNet. Full sources and licences.