En route inefficiency is measured in terms of extra distance flown by an aircraft, above a benchmark distance that relates to the theoretical shortest distance route (great circle route). In this paper, we have explored causal relations among en route inefficiency with multiple identified sources: convective weather, wind, miles-in-trail (MIT) restrictions, airspace flow programs (AFPs) and special activity airspace (SAA). We propose two mechanisms – strategic route choice and tactical reroute – to ascribe flight en route inefficiency to these factors. In our framework, we first propose an efficient trajectory clustering algorithm to identify nominal routes that reveal both air traffic flow patterns and air route structures in the national airspace system. Second, we develop a tree-based searching algorithm that matches different causal factors to the identified nominal routes in a 4-dimensional manner. Third, we employ a discrete choice modeling framework to quantitatively understand the flight route choice process, and establish a linear model to understand the tactical reroute process. Finally, we estimate the contributions of the identified causal factors to flight inefficiency through counterfactual analysis. Numerical experiments based on 8 representative airport pairs suggest strong negative impact of convection and headwind on route choice process, while MIT, AFP and SAA only demonstrate negative effects on some pairs. We have also shown that the contributions of convective weather, wind, traffic management initiatives, and SAA are up to 7.1%, 14.0%, 4.4%, 21.9%, respectively.

航路效率低下是根据飞机飞行的额外距离来衡量的，高于与理论最短距离航线（大圆航线）相关的基准距离。在本文中，我们探讨了航路效率低下与多个确定来源之间的因果关系：对流天气、风、飞行里程 (MIT) 限制、空域流量计划 (AFP) 和特殊活动空域 (SAA)。我们提出了两种机制——战略路线选择和战术改道——将飞行途中的低效率归因于这些因素。在我们的框架中，我们首先提出了一种有效的轨迹聚类算法来识别标称航线，这些航线揭示了国家空域系统中的空中交通流模式和航线结构。第二，我们开发了一种基于树的搜索算法，该算法以 4 维方式将不同的因果因素与已识别的标称路线相匹配。第三，我们采用离散选择建模框架来定量理解飞行路线选择过程，并建立线性模型来理解战术改道过程。最后，我们通过反事实分析估计了已识别的因果因素对飞行效率低下的贡献。基于 8 个具有代表性的机场对的数值实验表明对流和逆风对路线选择过程产生了强烈的负面影响，而 MIT、AFP 和 SAA 仅对某些对显示出负面影响。我们还表明，对流天气、风、交通管理举措和 SAA 的贡献分别高达 7.1%、14.0%、4.4%、21.9%。