In this what-if, each line grows today's seat-miles at an assumed rate of economic growth times the income elasticity. Seat-miles measure the capacity airlines fly, not the number of aircraft they need.
What this shows: The chart covers 2005 to 2044. It plots Observed (T-100, US carriers), GDP growth 2.5% a year (central), GDP growth 1.5% a year, GDP growth 3.5% a year, GDP growth 0.5% a year and GDP growth -0.5% a year on a vertical axis of Available seat-miles (billions). Latest value: Observed (T-100, US carriers) 1,353. Projected to 2044: GDP growth 2.5% a year (central) 2,152; GDP growth 1.5% a year 1,790; GDP growth 3.5% a year 2,583; GDP growth 0.5% a year 1,486; GDP growth -0.5% a year 1,231. Observed data run through 2024; the chart extends to 2044 with projected values.
Conditions and method
Status: projection (capacity paths translated from macro scenarios at a fixed elasticity, not an independent demand forecast).
Each line is a scenario, one per assumed GDP growth rate. The spread between them is not a confidence band.
This chart is a constant-elasticity translation of assumed GDP growth into seat-miles: 2.5% a year times an elasticity of 0.94, about 2.35% a year over 2024-2044. The site’s income-model projection counts passengers and grows them about 0.93% a year over 2025-2044. Of the 1.4 points between the two rates, 0.5 is the GDP assumption (the projection’s own path grows 1.99% a year, giving 1.87% at 0.94) and 0.9 the projection’s saturating curve, which responds less to income.
Each path compounds observed 2024 US-carrier seat-miles (1,353 billion, T-100) at an assumed GDP growth rate multiplied by the US income elasticity of passenger demand (0.939). No productivity or load-factor term enters: seat-miles are assumed to move in step with passengers.
The GDP growth rates are assumptions, and no source for them is cited in this project. Each path holds one rate for all 20 years (3.5%, 2.5%, 1.5%, 0.5%, -0.5% a year). The lines are named for their rate because a low rate held for 20 years is not a recession followed by a recovery. The central path is this chart’s own choice of rate.