A Highflying Growth Strategy pays off for United

Airlines can't easily add more places and still demand more for them, but United just seems to do that. The strategy is risky, but investors can underestimate the chance of success.

After US markets closed on Tuesday, United Continental Holdings said the first-quarter earnings doubled compared to the same period in 2018, surpassing analysts' expectations. The company's shares rose almost 4% when the market reopened on Wednesday.

Revenue …