From Longman Dictionary of Contemporary Englishfly-by-nightˈfly-by-ˌnight adjective [only before noun] informal BBa fly-by-night company or businessman is one that you cannot trust because they have only been in business for a short time and are only interested in making quick profits
Examples from the Corpus
fly-by-night• Not the richest of pickings, usually left to the fly-by-night minicabs.• He also insists that it won't be a fly-by-night operation, that his commitment to the community is lasting and genuine.• This would solve the problem of fly-by-night organisers.From Longman Business Dictionaryfly-by-nightˈfly-by-night adjective [only before a noun] informal a fly-by-night company or businessperson is not reliable and is only interested in making a quick profit and then disappearingThe authority requires surety bonds of $50,000 from health agencies to deter fly-by-night operations from joining the program. 