Catalyzes the oxidation of long-chain aliphatic aldehydes to acids. May be implicated in controlling luminescence as it catalyzes the oxidation of the fatty aldehyde substrate for the light-emitting reaction. an aldehyde + H2O + NADP(+) = a carboxylate + 2 H(+) + NADPH Homodimer. Belongs to the aldehyde dehydrogenase family.