Globalisation, with its concomitant rise in international merger activity, allied to the proliferation of merger control regimes vetting such activity, increases the likelihood of two or more competition authorities reaching divergent decisions in the same case. This article reveals that this situation arose in the proposed merger between two US-based companies, General Electric (GE) and Honeywell, with the EU prohibiting the merger, and the US Department of Justice approving it. Further, it discusses the analytical and interpretational differences which led to those divergent outcomes. The analytical debate centres on the appropriateness of the two theoretical approaches used to assess proposed mergers, with the EU using the range effects of competitive harm approach and the US giving greater weight to an economic efficiencies merger defence. The fallout from the GE/Honeywell case has given added impetus to progress analytical convergence in relation to the vetting of international mergers. This has found expression at the multilateral level, which links to EU initiatives. The article predicts that the EU is highly likely to incorporate an economic efficiencies defence into its merger control law, bringing it into line with other key players. Of course, analytical convergence cannot guarantee that interpretational differences will not arise, as was evident in aspects of the GE/Honeywell case.