Influenza vaccine strains (IVS) contain the hemagglutinin (HA) and neuraminidase (NA) genome segments of relevant circulating strains in the genetic background of influenza A/PR/8/1934 virus (PR8). Previous work has shown that the nature of the PB1 segment may be a limiting factor for the efficient production of IVS. Here, we show that the PB1 segment (PB1Gi) from the 2009 pandemic influenza A virus (IAV) A/Giessen/06/2009 (Gi wt, H1N1pdm) may help to resolve (some of) these limitations. We produced a set of recombinant PR8-derived viruses that contained (i) the HA and NA segments from representative IAV strains (H3N2, H5N1, H7N9, H9N2), (ii) the PB1 segment from PR8 or Gi wt, respectively, and (iii) the remaining five genome segments from PR8. Viruses containing the PB1Gi segment, together with the heterologous HA/NA segments and five PR8 segments (5+2+1), replicated to higher titers compared to their 6+2 counterparts containing six PR8 segments and the equivalent heterologous HA/NA segments. Compared to PB1PR8-containing IVS, viruses with the PB1Gi segment replicated to higher or similar titers in both cell culture and embryonated eggs, most profoundly IVS of the H5N1 and H7N9 subtype, which are known to grow poorly in these systems. IVS containing either the PB1Gi or the cognate PB1 segment of the respective specific HA/NA donor strain showed enhanced or similar viral replication levels. The study suggests that substitution of PB1PR8 with the PB1Gi segment may greatly improve the large-scale production of PR8-derived IVS, especially of those known to replicate poorly in vitro.