thin
Of a route: relatively little used.
thin: a route where demand barely justifies service
A thin route in aviation is one where passenger demand, cargo volume, or both are too low to support frequent service or full-size aircraft profitably. Airlines operate these routes with smaller turboprops or regional jets, often on a daily or a few-times-weekly schedule. A thin route might connect a regional hub to a smaller city 200 to 400 miles away, serving business travelers, connecting passengers, and occasional leisure traffic. The economics are fragile: load factors must stay high, fuel costs must stay low, and competition must stay away.
Airlines classify routes by demand density and revenue potential. Thin routes sit well below the profitable threshold for mainline narrow-bodies like the 737 or A320. They require smaller aircraft to hold unit costs down, which means airlines typically assign 50 to 90 seat regional jets or 30 to 70 seat turboprops. On a thin route, a regional carrier or a major airline's regional subsidiary often operates the service under a capacity purchase agreement with the major carrier, which sells the seats.
Why thin routes matter and break
Thin routes are vulnerable. A single competitor, a fuel spike, or economic contraction can tip them into loss. Many thin routes exist because of subsidies, regulatory requirements, or network strategy rather than standalone profit. Some are subsidized by the U.S. Essential Air Service program or equivalent schemes in other countries, guaranteeing a minimum service level to communities that might otherwise lose air access.
From a maintenance standpoint, thin routes create scheduling challenges. Aircraft must turn fast and carry high utilization to pay for their fixed costs, which means compressed maintenance windows and pressure to keep aircraft in service. Parts availability for regional turboprops and jets can lag behind mainline fleets, and downtime on a thin route can mean empty seats for days.
The term reflects operational reality, not judgment. Thin routes are not inherently bad: they connect communities, generate employment, and sustain regional carriers. But they demand discipline in cost control, ruthless asset management, and often external support to survive.