Fibroblast Growth Factor Receptor (FGFR) signaling pathway is initiated by the binding of secreted FGFs - bnl or ths/pyr to receptor tyrosine kinases btl or htl, respectively, to initiate signaling primarily via the canonical Ras/Raf/MAP kinase (ERK) cascade. FGFR signaling is important in several morphogenic events in Drosophila, notably during mesoderm and tracheal development. (Adapted from FBrf0221038).