The novel multi remote tower concept involves the control of two airports by one tower controller from one remote workplace at a time. In order to implement a multi remote tower into operations, a safety assessment is crucial to evaluate existing risks. Since there is currently no operational experience available concerning this concept, the hazard identification and risk mitigation remains hypothetical. However, empiric data is needed for evaluating and focusing on the safety-relevant hazards that are multi remote tower specific. To close this gap, we developed the MERASSA concept for gaining evidence on the safety-relevance of hazard using Human-In-The-Loop simulations and stress test scenarios. The method was assessed through a validation study at the multi remote tower case using eight identified hazards that are human-issue originated. In total 32 simulation runs with eight rated and experienced tower controllers were carried out. The results of the study show the ability of the tower controller to compensate risk by slowing down the work speed. No hazard could be verified through a comparison of the multi and single runway baseline scenario. Additionally, the results indicate a clear lack of confidence of the tower controller to control two airports at a time due to the need to share attention across the work environment. The comparison of the empiric and subjective results show equal trends which are a sign for the success of applying the method. However, a major drawback of using simulations and stress test scenarios are the enormous efforts needed to control the conditions of testing