Microstructural features have been investigated in fusion welded samples of the established At-Cu-Mg-Mn airframe alloy, 2024-T351. Specifically, the local strengthening and precipitate conditions have been assessed for variable polarity plasma are (VPPA) welding of 13mm thick plate. Microstructures were studied using a combination of differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). Micro-hardness measurements (Vickers hardness) were carried out, identifying a two peak structure in the heat affected zone (HAZ) and a minimum plateau in the fusion zone. The influences of aging, re-solutionising and re-precipitation are noted across the HAZ, along with the incidence of the Omega(Al2Cu) phase.