How Airlines Balance High Revenue with Thin Margins

Big Revenue, Small Profit

Airlines are among the most visible businesses in any economy. Their revenue is large, their brands are familiar and their fleets cost billions. Yet across the world, and especially in India, airlines have a long history of thin margins and frequent failures.

The reason is not that airlines are badly run. It is that their profit is a small difference between two large numbers, and both numbers move with things the airline cannot control.

The Two Numbers That Run an Airline

The industry measures everything per available seat-kilometre (ASK): one seat flown one kilometre, whether or not anyone sits in it.

• RASK is revenue per ASK.
• CASK is cost per ASK.

Operating profit = (RASK - CASK) × ASKs

RASK depends on the fare per passenger-kilometre (the yield) and on how full the planes are (the load factor):

RASK = Yield × Load factor

A Worked Example: Small Changes, Large Effects

Illustrative example. An airline flies 50 billion ASKs a year. Its RASK is ₹5.00 and its CASK is ₹4.75.

• Revenue: ₹25,000 crore
• Operating profit: ₹1,250 crore, a 5% margin

Fuel rises 25%. Fuel is 40% of costs, so CASK rises by 10%, to about ₹5.23. The airline now loses about 4.5% on every rupee of revenue. A ₹1,250 crore profit becomes a loss of over ₹1,100 crore, with the same planes, routes and passengers.

Load factor falls from 87% to 82%. At the same yield, RASK falls from ₹5.00 to about ₹4.71, below CASK. Five empty seats in every hundred turn a profitable airline into a loss-making one.

This is what thin margins mean in practice.

Costs Airlines Cannot Control

• Fuel. Aviation turbine fuel (ATF) is the largest single cost, close to 40% of operating costs for Indian airlines. Its price follows crude oil, and India also adds state taxes on ATF.
• The rupee. Aircraft leases, maintenance contracts and part of fuel costs are priced in dollars. A weaker rupee raises costs even when nothing else changes.
• Airport and navigation charges, which are set by regulators and airport operators.

Revenue, by contrast, is in rupees for domestic flights, and fares are set in a competitive market.

High Fixed Costs and Perishable Seats

Once a flight is scheduled, most of its cost is fixed: the aircraft, crew, fuel for the trip and airport fees. An empty seat earns nothing and cannot be sold later. This pushes airlines to cut fares to fill seats, which can start price wars, especially when new capacity arrives faster than demand.

2026: A Stress Test in Real Time

The fuel shock of 2026 showed these mechanics clearly. As crude oil prices surged, domestic ATF prices rose from about ₹80,000 per kilolitre to more than ₹1 lakh in many cities. On 1 April 2026, the central government capped ATF price increases for domestic operators at 25%, and some states cut their taxes on ATF.

Airlines responded by cutting capacity. From June, Air India planned to cut up to 15% of its domestic flights and IndiGo 5% to 7% for 90 days. Domestic passenger traffic in August 2026 was about 6% lower than a year earlier. IndiGo's domestic market share was 65% that month, and the Air India group's 26.7%, a market far more concentrated than a decade ago.

Fuel Charges and Pricing Power

Airlines try to pass fuel costs on to passengers through fuel charges added to fares. IndiGo, for example, revised its fuel charges on domestic and international flights from 6 October 2026. Whether such charges stick depends on competition. When one or two airlines carry most passengers, fare increases are easier to hold. When many airlines chase the same routes, someone usually breaks ranks.

India's market today is far more concentrated than it was ten years ago, with one airline carrying about two-thirds of domestic passengers. That gives the leaders more room to protect margins than in past fuel shocks. It also means a disruption at one large airline affects most of the country's flyers, and it draws closer attention from regulators.

A History of Failures

India's aviation history includes several major failures: Kingfisher Airlines stopped flying in 2012, Jet Airways in 2019 and Go First in 2023. The causes differed, but the pattern was similar: thin margins, high fixed costs, heavy debt and leases, and too little cash to survive a bad stretch.

Leases and Hidden Leverage

Most Indian airlines lease their aircraft rather than own them. Since Ind AS 116, these leases appear on the balance sheet as lease liabilities. For airlines, they are often much larger than bank borrowings.

So an airline that reports little "debt" may be heavily leveraged once leases are counted. When comparing airlines, include lease liabilities in enterprise value and use EBITDA that excludes lease rentals, consistently.

Habits for Reading Airline Results

1. Track RASK, CASK and the spread between them each quarter.
2. Split CASK into fuel and non-fuel costs. Non-fuel CASK shows how efficient the airline is.
3. Watch load factor and yield separately.
4. Include lease liabilities in any measure of leverage or EV.
5. Check cash and liquidity, since a bad quarter can arrive with little warning.

The Reframe

An airline's revenue tells you how big it is. The gap between RASK and CASK tells you whether it will survive. That gap is small, and it is set as much by oil markets and currencies as by the airline itself.