The process that gives rise to the apical ectodermal ridge. This process pertains to the initial formation of a structure from unspecified parts. [ http://www.ncbi.nlm.nih.gov/pubmed/9596583 http://www.ncbi.nlm.nih.gov/pubmed/18359901 http://purl.obolibrary.org/obo/go/references/0000081 http://www.ncbi.nlm.nih.gov/pubmed/9323126 ]