The best-performing stock in the Dow this year is rallying on blockbuster earnings

Boeing's stock is flying high after a second-quarter earnings that smashed expectations.

The highlight of the planemaker's report was free cash flow that climbed above $4.5 billion, more than double analyst expectations. And in an effort to sweeten the pot for loyal shareholders, the company used $3.4 billion of that to buy back shares and pay out dividends.

The resulting 3.6% increase in pre-market trading extends Boeing's outperformance relative to its peers in the 30-stock Dow Jones Industrial Average. Shares are up 36% year-to-date, the most in the equity benchmark - even more than red-hot Apple. That's also more than triple the Dow's return in 2017.

The company, which has the second-largest weighting in the Dow, has been the biggest contributer to the gauge this year, accounting for more than 400 points of its 1,825-point net move.

Boeing bulls will be further emboldened by the company's decision to raise its year-end earnings forecast to $9.80 to $10 a share, a 60-cent increase.

They'll also find comfort in the record backlog of orders for Boeing's single-aisle 737 aircraft, which is currently the company's biggest driver of profits.

The continued bullishness on Boeing is being reflected in short seller activity. Short interest - a measure of bets that share prices will drop - sits at 1.4% of shares outstanding, according to data compiled by IHS Markit. That's close to the measure's 2017 low, reached earlier this month.

Get the latest Boeing stock price here.