  We discuss the relation between remnant fragmentation in inelastic
high-energy hadronic interactions and muon production in extensive cosmic ray
air showers. Using a newly developed tool, a simple and flexible hadronic event
generator, we analyze the forward region of hadronic interactions. We show that
measurements of the Feynman-x distribution in the beam fragmentation region at
LHCf will be key to understanding muon production in air showers
quantitatively.
