X‐ray diffraction data collected at cryogenic temperatures from flash‐cooled crystals of influenza virus hemagglutinin show improvements in both resolution and quality relative to data collected at 277 K. These improvements are dramatic for flash‐cooled hemagglutinin crystals irradiated with X‐rays from a synchrotron source. At the Cornell High Energy Synchrotron Source flash‐cooled hemagglutinin crystals diffracted at least 0.9 Å farther than hemagglutinin crystals at ambient temperatures. Radiation damage in the flash‐cooled crystals is reduced, making it possible to collect a complete data set from a single hemagglutinin crystal. However, radiation damage is not eliminated in the flash‐cooled crystal. As a result the quality of X‐ray data can be significantly degraded during long exposure times at