GO:0044458

The assembly of a motile cilium, a cilium that contains a regular longitudinal array of axonemal microtubules. In vertebrates, motile cilia are usually formed around a 9 + 2 microtubule core structure. Motile cilia are often found in tissues where propagation of fluid is necessary for proper organ development or function. [PMID:21129373, ZFIN:dsf]