  We show that all features of the ultrahigh energy cosmic ray spectrum from
10^{17} eV to 10^{21} eV can be described with a simple power-like injection
spectrum of protons under the assumption that the neutrino-nucleon
cross-section is significantly enhanced at center of mass energies above
\approx 100 TeV. In our scenario, the cosmogenic neutrinos produced during the
propagation of protons through the cosmic microwave background initiate air
showers in the atmosphere, just as the protons. The total air shower spectrum
induced by protons and neutrinos shows excellent agreement with the
observations. A particular possibility for a large neutrino-nucleon
cross-section exists within the Standard Model through electroweak
instanton-induced processes.
