The key reason is that the low-cost airline industry in Europe still has scope to take market share from the old national monopolists. This trend is hardly new - which is why easyJet's shares have generated an almost fivefold return since flotation in 2000 - but nor is it mature. The Luton-based carrier controls about 20 per cent of the UK and 23 per cent of the Swiss markets. But elsewhere in Europe the airline scene looks more like it used to in Britain, with incumbent flag-carriers still dominant.
Take Germany: a recent survey on behalf of Liberum, the stockbroker, found that consumers in Europe's largest economy rated local airlines - Lufthansa, its low-cost brand Germanwings and Air Berlin - well above easyJet and Ryanair for value for money. But as Liberum analyst Gerald Khoo points out, neither Air Berlin nor Germanwings are profitable operations, so their prominence may not be sustainable. The small corner of the market currently occupied by easyJet (with market share of 4 per cent) and Ryanair could therefore grow substantially. Having established a new base in Hamburg in 2014, easyJet increased its German capacity by 15 per cent during the year to September with the launch of 16 new routes.
The reason to buy shares in the orange-liveried airline founded in 1995 by Sir Stelios Haji-Ioannou, rather than those of its Irish rival, boils down to valuation. Relative to expected profits, easyJet's shares trade at a discount both to their own trading history and to those of Ryanair - as the graph below shows. It is hard to come up with a convincing explanation for why this is the case.
So what could go wrong? In a 2002 interview with the Telegraph, Mr Buffett cited three problems with airline investments: high fixed costs, strong labour unions and "commodity pricing".
In the case of easyJet, it is easy to dismiss the point about labour unions, which have been an advantage to the low-cost carriers in their battle with legacy operators. On fixed costs Mr Buffett has a point. UK airlines have been able to increase their profits dramatically over the past three years by filling up their planes in an environment of strengthening demand. But those gains would reverse just as dramatically if consumer and business sentiment took a turn for the worse.
However, my base assumption is that the low-cost carriers will be bigger in five years' time than they are now. Market share gains at the expense of the legacy European flag-carriers, and some structural growth in demand in line with past trends, should - on a five-year view - trump the vagaries of the business cycle. For the same reason I am not too worried about temporary disruptions as a result of the weather, traffic-control strikes or terrorist attacks such as we have seen this year. Volatility is par for the course for airline investing, but it is not incompatible with growth.
What Mr Buffett called commodity pricing is a more deep-seated problem. The low-cost carriers owe their success to the weakening of consumer ties to establishment brands like British Airways. But the same trend exposes them to vicious competition on price. This is particularly true when airline backers - such as the United Arab Emirates' Etihad Airways, a key shareholder in both Air Berlin and Italian flag-carrier Alitalia - have a high tolerance for losses. EasyJet expects revenues per seat to dip in its financial year to September 2016 as airlines compete to pass falling fuel costs on to their customers.
Yet capacity growth funded by strong operating cash flow will still drive bottom-line growth. The problems of a commoditised product will only really come to the fore when the market share gains that have fuelled the low-cost carriers for the past two decades peter out. That point still looks a long way off. Meanwhile, easyJet's shares look a steal on 11 times forward earnings.
