Integrating employee groups from separate firms into a combined, well-functioning workforce presents one of the most difficult challenges in a corporate merger. This has particularly been the case in the recent airline mergers in the U.S. that have left three large legacy airlines, namely, American, Delta, and United. Carriers in these mergers have, in some cases, seen years of arbitration and litigation, employee turmoil and labor union decertification, and delays in operational integration and the realization of anticipated merger synergies. In response to this situation, this report introduces seniority_list, a computer-based tool that can be used by unions, employee groups, arbitrators, airlines, and consultants in their workforce integration efforts, analyses, and recommendations. The report demonstrates how the tool addresses such variables as employee tenure, jobs available, and furlough recall schedules, together with ordering and conditions on integration alternatives, to comprehensively assess the short- and long-term impact of workforce integration strategies. The purpose of seniority_list is to help speed up post-merger labor integration, enhance outcome fairness for merged employee groups, reduce conflict, and allow airlines to more quickly realize the operational and financial benefits expected from a merger.