Here, we report a systematic investigation of the role of the first four AUG codons in segment 2 in directing viral protein synthesis. Our findings indicate a modified leaky scanning model in which translation initiation at internal start codons is influenced by upstream AUGs, but where sORF2 is a critical regulatory element that depresses PB1-F2 synthesis but promotes N40 translation through a reinitiation mechanism. Unexpectedly, we also found that the translational regulatory sequences surrounding AUGs 1 and 2 overlapped with sequences required for packaging of the segment into virus particles, providing an interesting insight into the evolutionary constraints acting on this section of the viral genome.