Catalyzes the adenylation of flavin mononucleotide (FMN) to form flavin adenine dinucleotide (FAD) coenzyme. ATP + FMN + H(+) = diphosphate + FAD Cofactor biosynthesis; FAD biosynthesis; FAD from FMN: step 1/1. The molybdenum cofactor biosynthesis protein-like region may not be functional. In the N-terminal section; belongs to the MoaB/Mog family. In the C-terminal section; belongs to the PAPS reductase family. FAD1 subfamily.