The Highs And Lows Of Investing In The Airline Industry

10 mins

The Highs And Lows Of Investing In The Airline Industry

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The airline industry is one of the most fascinating sectors of the modern economy, and one of its most essential. Its companies can be broadly classified into two categories: no-frills low-cost carriers and the full-service firms with complimentary meals, premium cabin options, and sought-after loyalty programs.

The postwar economic and technological boom saw global air passenger traffic inexorably increase to hit 4.6 billion passengers in 2019. And then came coronavirus. The pandemic slammed the industry particularly hard, more than 9/11 and the 2008 financial crisis put together: airlines around the world made an estimated $118 billion loss in 2020.

But as the chart below shows, the airline industry overall was previously enjoying healthy profitability. In fact, the past decade was the most profitable in its history.

The airline industry was consistently profitable throughout the 2010s (Source: Statista)
The airline industry was consistently profitable throughout the 2010s (Source: Statista)

While several airlines have gone bankrupt as a result of the pandemic, many have managed to weather the storm – and may arguably come out of it stronger than ever, with government aid in their pockets and less competition around. The S&P 500 Airlines Industry Index, however, has yet to resume its pre-2020 altitude.

So assuming airlines can return to their previous profitability, now might be a great time to get on board with a few of their stocks – and this Pack is all about arming you with the analytical tools you’ll need to find the very best opportunities out there. Buckle up…

How to analyze airline companies

Before diving into the industry-specific metrics used by professionals and the airlines themselves to evaluate financial performance, let’s take a step back and ask ourselves about the main factors driving an airline’s profitability. First, how much capacity does it have in terms of flights per year? Second, how much of that capacity is being utilized in terms of seats filled? Third, and most importantly of all, how much revenue is the airline generating per passenger – and how does that compare to the cost of operating its flights?

A commonly used measure of airline capacity is available seat miles (ASM), which is calculated by multiplying the number of seats available on a flight by the number of miles traveled, regardless of whether the seat was occupied or not. So a plane with 100 seats that flies 300 miles generates 100 x 300 = 30,000 ASM. Adding that up across all of an airline’s flights in a particular time period – say a quarter or a year – gives you a total ASM figure. Delta Air Lines’ 2019 ASM, for instance, was 275 billion. Changes over time can be illuminating: a growing ASM indicates that the airline is making either more or longer flights – or both.

But an airline’s passenger volume is probably more important for investors than capacity. To measure this, you can work out revenue passenger miles (RPM), which is calculated by multiplying number of paying passengers by distance traveled. 80 paying passengers on board a 200-mile flight would therefore generate 80 x 200 = 16,000 RPM. Once again, you can aggregate that for all of an airline’s flights in a particular time period: in 2019, Delta notched 238 billion total RPM.

Dividing RPM by ASM gives you something called load factor, which measures an airline’s capacity utilization: the percentage of available seating capacity that’s being filled by passengers. Dividing Delta’s 2019 RPM of 238 billion by its annual ASM of 275 billion works out at a (238 / 275) x 100 = 87% load factor. In other words, the average Delta flight was 87% full in 2019.

In general, a high load factor is clearly better than a low one. There are lots of fixed costs involved in operating a flight: airport fees, pilot salaries, fuel costs, and so on. So a flight that’s filled with few paying passengers is a poor use of airline resources, and will likely be loss-making – even more so if it’s a long-haul trip. Load factor, of course, already takes distance traveled into account.

If load factor tells you how full an airline is packing its planes, then the obvious next question is how much revenue it’s generating per passenger. But in order to make accurate comparisons, it’s even better to look at revenue per passenger per mile: after all, a flight’s fare is often proportional to its length.

You can use passenger yield to easily assess an airline’s average fare per passenger per mile. It’s calculated by dividing total passenger revenue by revenue passenger miles (RPM). So if Delta Air Lines generated $42 billion in passenger revenue in 2019 and flew 238 billion RPM in 2019, its passenger yield was 42 / 238 = $0.176. Put simply, Delta took in 18 cents on average for each mile it flew each passenger. The higher an airline’s passenger yield, the better – with the caveat that you’d naturally expect highfalutin full-service carriers to have greater yields than low-cost carriers.

But while passenger yield helps you assess an airline’s revenue-generating potential, you still need to factor in the airline’s costs to paint a picture of its profitability. Enter our last metric (promise): cost per available seat mile (CASM), which is calculated by dividing total operating costs by available seat miles (ASM). That makes sense when you think about it: the cost of operating a flight is largely determined by the size of the plane and the distance flown, both of which ASM captures.

Returning to our Delta Air Lines example, the firm had $40 billion of operating costs and 275 billion ASM in 2019. 40 / 275 = $0.145: so in 2019, Delta spent around 15 cents on average flying each seat each mile.

What comprises an airline’s operating costs? The three main things are labor, maintenance, and fuel. All three are variable costs in the sense that an airline’s total spending on them is largely determined by the number of flights it operates in any given year. But fuel costs are also heavily influenced by oil prices: largely beyond an airline’s control, outside of its fuel hedging policy. For that reason, you’ll sometimes see airlines report an additional CASM figure excluding the cost of fuel and allowing investors to better isolate and directly compare operating costs across companies.

How to pick airline stocks

Now for the juicy part. You can find the metrics discussed above in airline companies’ financial statements and investor presentations, so you’ll never have to worry about calculating them yourself. But now that you know what they are and how to interpret them, you can start using these metrics to analyze airline stocks. Obviously comparisons are key here, over time and between companies – so check out the MIT Airline Data Project to get past and present figures for all the major US airlines in one place.

As an investor, what do you want to see in an airline company? Capacity growth, as seen in available seat miles (ASM) expansion, is a good place to start. But you don’t want an airline to be opening up half-empty routes. That’s where load factor comes in: capacity utilization that’s increasing and/or is higher than peers’ is always preferred. A high load factor indicates that an airline is using its available capacity efficiently and isn’t leaving any money on the table – or rather, on an empty seat.

The next thing to assess is passenger yield. If an airline can steadily increase average per-mile fares over time without losing customers – that is, while maintaining a stable or growing number of revenue passenger miles (RPM) – then that’s a very good sign. Passenger yield can be negatively affected by cut-throat competition with regional rivals, especially among low-cost carriers – but strong reputations and loyalty programs can help shore yields up. It’s therefore worth looking into these less intangible aspects of the airline, and even talking to friends who’ve flown with it about their own experience.

Finally, you can use cost per available seat mile (CASM) to suss how well an airline is managing its outgoings. A decreasing CASM indicates that the airline is becoming more cost-efficient, while a figure lower than others indicates that it’s already got a well-kept fleet. Still, you’d expect low-cost airlines to have lower CASMs than their full-service peers, so be sure you’re comparing apples to apples. An ideal scenario is one where an airline’s increasing its passenger yield over time while lowering its CASM. The widening gap between the two translates to higher profit margins: something you always want to see as an investor.

Let’s try putting all this into practice. The biggest three US airlines are American Airlines, Delta Air Lines, and United Airlines. The graph below shows their stock price performances in 2019. You can see that Delta performed best, up 17% over the course of the year while United rose 5% – and American’s shares fell 11%.

2019 stock price performance of the biggest three US airlines (Source: Koyfin)
2019 stock price performance of the biggest three US airlines (Source: Koyfin)

To analyze the reasons for this divergent price performance, let’s now take a look at the airlines’ 2019 performance on the metrics we’ve been considering above, as collated in the table below.

The biggest three US airlines compared using industry-specific metrics
The biggest three US airlines compared using industry-specific metrics

Delta Air Lines – the top-performing stock among the three – had plenty going for it in 2019. For starters, it had the highest capacity increase, with ASM increasing 5.3%. And that didn’t come at the expense of empty planes: Delta also had the highest load factor, indicating it was the best at efficiently utilizing its capacity. Delta had the highest passenger yield too, meaning it generated the most revenue per passenger per mile. While the company’s CASM wasn’t the lowest of the bunch, at least Delta managed to reduce it compared to 2018 – unlike American Airlines. That yawning CASM was likely one reason why American’s stock price fell in 2019.

The key takeaway from this example is that airlines performing well on the metrics you’ve learned about should, in theory, see strong stock price performances too. Which brings us to our last question: after you’ve analyzed an airline company, how can you assess the stock’s valuation?

Comparing valuation multiples between peers is one popular approach: an airline company with better operational metrics than its rivals but a lower multiple means you just might be onto something. The most common valuation multiple applied to airline stocks is EV/EBITDA. Enterprise value (EV) is the value of a company’s outstanding shares plus its “net debt” – total debt minus cash holdings. It’s essentially what someone would have to pay to buy the entire company. EBITDA, on the other hand, means “earnings before interest, taxes, and depreciation and amortization”. This essentially calculates a company’s operating profit prior to factoring in the impacts of various financing and accounting decisions.

You can find airline stocks’ EV/EBITDA multiples for free via data sources such as Atom Finance and Koyfin. Where possible, it’s better to look at the multiple that uses “NTM” – or next twelve months – EBITDA, as this uses analysts’ average forecasts for future operating profit rather than backward-looking numbers.


Finimize crew, prepare for landing: you’ve now got a pretty good grounding in how to analyze airline companies like a pro and what to look out for when selecting specific airline stocks. Now get out there and put what you’ve just learned into practice – you might just find your next high-flying stock emerges, phoenix-like, from a resurgent airline industry.

In this Pack, you’ve learned:

🔹 The airline industry consists of two distinct categories: low-cost and full-service carriers.

🔹 Available seat miles (ASM) measures an airline's capacity. A growing ASM indicates that the airline is making either more or longer flights, or both.

🔹 Load factor tells you what percentage of an airline's available seating capacity is being filled with passengers: the higher, the better.

🔹 Passenger yield gives you an indication of the average fare per passenger per mile. It’s a promising sign if an airline can steadily increase this over time without losing customers.

🔹 Cost per available seat mile (CASM) tells us how well an airline is managing its costs. A low or decreasing CASM compared to rivals indicates that the airline is or is becoming more cost-efficient.

🔹 The most common valuation multiple applied to value airline stocks is EV/EBITDA. If you find an airline with better operational metrics than its peers but a lower valuation multiple, then you just might be onto something.

Now put your newfound knowledge to the test with our quiz.



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Disclaimer: These articles are provided for information purposes only. Occasionally, an opinion about whether to buy or sell a specific investment may be provided. The content is not intended to be a personal recommendation to buy or sell any financial instrument or product, or to adopt any investment strategy as it is not provided based on an assessment of your investing knowledge and experience, your financial situation or your investment objectives. The value of your investments, and the income derived from them, may go down as well as up. You may not get back all the money that you invest. The investments referred to in this article may not be suitable for all investors, and if in doubt, an investor should seek advice from a qualified investment advisor.

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