The single known species of segment 2 mRNA produces three proteins: PB1, PB1-F2 and PB1-N40. PB1 is an essential protein, encoding the potential antiviral drug target of an RNA polymerase, while PB1-F2 modulates pathogenicity in some host-virus combinations and the function of N40 is unknown. Despite representing the only known functionally tri-cistronic influenza virus mRNA, the mechanisms that control protein expression from the segment have not been fully elucidated. Here, we confirm the hypothesis that leaky ribosomal scanning has a role in mediating expression of PB1-F2 and PB1-N40. However, this mechanism does not fully explain segment 2 translation and we also identify ribosomal reinitiation after sORF2 as important for PB1-N40 expression.