The flat-spectrum-radio-quasar 3C 454.3 underwent an extraordinary outburst in December 2009 when it became the brightest gamma-ray source in the sky for over one week. Its daily flux measured with the Fermi Large Area Telescope at photon energies E > 100MeV reached 22 ± 1 × 10−6 ph cm−2 s−1. It again became the brightest source in the sky in April 2010, triggering a pointedmode observation by Fermi. The γ-ray temporal and spectral properties during these exceptional events are presented and discussed
