Short answer: airlines do not evaluate a route only on the revenue of the passengers who fly it end to end. A thin route can be worth keeping because of the traffic it feeds into profitable long-haul flights, the airport slots it protects, the contracts it secures, or the competitor it keeps out.

Standalone profit is the wrong question

Ask whether a route makes money and you have to ask: measured how? A route's own P&L counts the fares of passengers flying that city pair. But on a hub-and-spoke network, a large share of the people on a regional flight are not going to the hub — they are going through it.

That is feed traffic, and its value is credited to the long-haul flight it fills, not the short one that delivered it. Kill the regional route and you do not just lose its small loss; you lose the connecting passengers who kept the widebody's load factor and fare mix healthy. Network planners measure this with profitability that allocates value across the whole itinerary, and routes that look hopeless standalone often look essential once you do.

The other reasons a loss-making route survives

Slots. At capacity-constrained airports — London Heathrow being the standard example — take-off and landing slots are scarce, extremely valuable, and subject to use-it-or-lose-it rules. Flying a marginal service to retain a slot portfolio can be entirely rational when the slot itself is worth far more than the annual loss on the route.

Defence. If a competitor establishes an unopposed presence in a market, it can build a base, a customer habit, and a cost position there. Continuing to fly a marginal route to deny that foothold is a strategic expense, not an operational mistake.

Corporate and contract commitments. Large corporate deals and government travel contracts are awarded on network coverage. Losing one city can put the whole contract at risk, and the contract's value dwarfs the route's loss.

Cargo. On some long-haul routes, belly cargo makes a material contribution that never appears in passenger metrics.

Subsidy and public service obligations. Many thin routes exist because a government pays for them — Essential Air Service in the United States, Public Service Obligation routes in Europe, and equivalent regional connectivity schemes elsewhere. The route is not commercial; it is procured.

Aircraft and crew positioning. Sometimes an aircraft simply has to be in a particular city tomorrow morning. Flying it with passengers, even at a poor fare, beats flying it empty.

Seasonality and maturity. New routes are typically given a ramp-up period — often measured in seasons, not weeks — because demand builds as the market learns the service exists. A route judged on its first quarter would almost never survive.

When airlines do cut

The tolerance is not infinite. A route usually goes when:

  • It fails to cover even its variable costs, so each departure loses cash;
  • The aircraft can earn materially more somewhere else — the opportunity cost test that drives most network reshuffles;
  • The strategic rationale expires (the slot rule changes, the contract is lost, the competitor withdraws);
  • Fuel or currency moves break the economics of a marginal long, thin sector.

That third bullet explains a lot of sudden-looking cuts. Nothing about the route changed; the reason it was being protected did.

Reading route announcements properly

When an airline launches a route that looks commercially odd, work through the list: is it feeding a hub bank? Protecting slots? Backed by a subsidy or a corporate contract? Blocking a rival? Positioning an aircraft? One of those is usually the answer, and it is rarely the one in the press release, which will talk about demand.

The takeaway

A route is a component in a network, not a standalone business. Judging it in isolation is like judging a loss-leader product without noticing the basket it fills. The interesting question is never "does this route make money" — it is "what would the network lose if this route stopped".