Airline stocks have been a popular investing theme over the past few years, as many of them have tripled, quadrupled or even quintupled in the past few years.

Yet investors are overlooking a crucial and highly successful behind-the-scenes industry player. Netherlands-based AerCap Holdings NV (NYSE: AER), the world’s largest aircraft lessor, is a stock that should be on your radar.

AerCap has been handily beating Wall Street earnings estimates, delivering as much as 65% upside during the past four quarters. Its stock, too, has been generating profits that make the S&P 500’s performance look meager.

Despite this stock’s massive gains, trailing and forward price-to-earnings ratios of only about 11 and 9, respectively, suggesting most investors still don’t have the stock on their radar.

That’s unfortunate. Without companies like AerCap, the airlines might not be looking at record profits. They’d have to own all of their own aircraft, and the added cost would hold them back.

#-ad_banner-#That’s why most airlines choose to lease at least a portion of their fleet. And for this, they’re turning increasingly to AerCap.

The company vaulted to the top of its industry a year ago with a $7.6-billion buyout of International Lease Finance Corp., a large leasing operation with more than 1,000 aircraft and roughly 200 customers worldwide.

Among the deal’s other key benefits: a $21-billion business backlog and the assumption of timely orders for sought-after aircraft from The Boeing Co. (NYSE: BA) and Airbus Group (OTC: EADSY) at substantial discounts.

International Lease Finance Corp. was previously owned by insurance giant American International Group, Inc. (NYSE: AIG), which has been divesting non-core businesses as part of its post-financial-crisis restructuring program.

Thanks to the buyout, AerCap now controls a fleet of more than 1,300 passenger planes. Most of these are company-owned, and a small number are managed on behalf of third parties.

The fleet consists mainly of half a dozen popular Airbus variants such as the A320, A330 and A350. It also includes more than 400 Boeing aircraft like the widely familiar 737, 767 and 777 models, as well as the 787. At less than eight years, the average age per aircraft is relatively young and fuel efficient.

Still, AerCap plans to buy hundreds of new aircraft in the coming years, as heavy demand related to air travel’s robust upswing has long kept fleet utilization near 100%.

The boom propelled AerCap to record results of its own, including almost a fivefold gain in annual revenue to $4.7 billion since 2012. Earnings have spiked nearly fourfold since 2012 to $4.54 per share.

Looking ahead, analysts project a continued surge in the demand for leased aircraft, and AerCap’s results reflect this. Last year, the number of new leases of company-owned aircraft more than doubled, while lease extensions rose nearly fivefold.

When it reported first-quarter performance on May 11, AerCap revealed that 368 new aircraft were on order with delivery dates spread over the next seven years. I expect these planes will be rapidly deployed when AerCap takes possession of them. Nearly all of those the firm is scheduled to receive through 2017 are already under lease or letters of intent to lease. Looking out to 2019, two-thirds of on-order aircraft already have customers waiting for them.

Because the air travel industry is cyclical, management purposely varies lease terms to blunt any unfavorable market conditions that may be present when contracts expire. Thus, leases typically range from about four-to-14 years. To minimize costs, the firm looks to extend expired contracts rather than take aircraft back and seek new customers to lease them.

With lease revenues soaring and global dominance established, AerCap should significantly beat its own estimate for record profits of $1 billion this year (up from $810 million in 2014). It already produced first-quarter adjusted net income of more than $300 million and could do even better in the remaining three quarters. Thus, I think AerCap can generate adjusted net income of at least $1.1-to-$1.2 billion in 2015.

Risks To Consider: AerCap’s $30 billion in debt represents markedly higher leverage than the industry average, and a substantial portion carries floating interest rates. This debt burden could become a major issue if interest rates shoot up unexpectedly and/or there’s a cyclical downturn that hurts the entire aircraft leasing industry.

Action To Take –> Don’t let the hype about airline stocks distract you from AerCap Holdings. It’s one of the air travel sector’s most promising investments.

Also, know that AerCap’s debt is manageable. Large chunks don’t start coming due for several years, and the firm makes it a priority to maintain ample liquidity for such obligations. Liquid assets currently include cash of $1.5 billion and about $7 billion remaining from financing arrangements. Operating efficiencies related to the International Lease Finance Corp. acquisition should enhance liquidity by reducing operating expenses by about $100 million per year.

This gives AerCap lots of elbow room to accumulate more cash and refinance some or all of its debt at favorable rates, which could persist a lot longer under an accommodative Federal Reserve. Thus, with its newfound market dominance and large backlog, AerCap should be very capable of delivering more double-digit profit growth and earnings beats in the coming years.

Stocks like AER are similar to a special group of securities we call “Forever Stocks.” These world-dominating companies control deep economic moats allowing them to fend off competitors. And they pay investors fat dividends while buying back massive amounts of stocks, which boosts the value of their remaining shares. These stocks are strong enough to buy, forget about and hold forever. To learn more about them — including some names and ticker symbols — click here.