This document discusses route profitability systems and challenges in airline cost accounting. It outlines a cost hierarchy including direct, indirect, fixed and variable costs. It also discusses system dependencies and different models for route profitability analysis from traditional to advanced. The advanced model allows for multi-level profit analysis for strategic, operational and managerial decisions. It emphasizes the need for a system that reconciles to financial reports in real-time and supports activity-based costing and planning/budgeting.