  Ultra high energy cosmic rays provide the highest known energy source in the
universe to measure proton cross sections. Though conditions for collecting
such data are less controlled than an accelerator environment, current
generation cosmic ray observatories have large enough exposures to collect
significant statistics for a reliable measurement for energies above what can
be attained in the lab. Cosmic ray measurements of cross section use
atmospheric calorimetry to measure depth of air shower maximum
($X_{\mathrm{max}}$), which is related to the primary particle's energy and
mass. The tail of the $X_{\mathrm{max}}$ distribution is assumed to be
dominated by showers generated by protons, allowing measurement of the
inelastic proton-air cross section. In this work the proton-air inelastic cross
section measurement, $\sigma^{\mathrm{inel}}_{\mathrm{p-air}}$, using data
observed by Telescope Array's Black Rock Mesa and Long Ridge fluorescence
detectors and surface detector array in hybrid mode is presented.
$\sigma^{\mathrm{inel}}_{\mathrm{p-air}}$ is observed to be $520.1 \pm
35.8$[Stat.] $^{+25.0}_{-40}$[Sys.]~mb at $\sqrt{s} = 73$ TeV. The total
proton-proton cross section is subsequently inferred from Glauber formalism and
is found to be $\sigma^{\mathrm{tot}}_{\mathrm{pp}} = 139.4 ^{+23.4}_{-21.3}$
[Stat.]$ ^{+15.0}_{-24.0}$[Sys.]~mb.
