  The interpretation of extensive air shower measurements, produced by
ultra-high energy cosmic rays, relies on the correct modeling of the hadron-air
interactions that occur during the shower development. The majority of hadronic
particles are produced at equivalent beam energies below the TeV range.
NA61/SHINE is a fixed target experiment using secondary beams produced at CERN
at the SPS. Hadron-hadron interactions have been recorded at beam momenta
between 13 and 350 GeV/c with a wide-acceptance spectrometer. In this
contribution we present measurements of the spectra of charged pions and the
$\rho^0$ production in pion-carbon interactions, which are essential for
modeling of air showers.
