Boeing reported a jump in fourth-quarter earnings on Wednesday and projected higher revenues and commercial aeroplane deliveries in 2018. Shares of the US aerospace giant jumped in pre-market trading after Boeing reported fourth-quarter profits of $3.1 billion, up 92 per cent from the year-ago period. Boeing forecast commercial plane deliveries of 810 to 815 this year, which would exceed the record 763 in 2017.

Earnings were bolstered by surging deliveries of the 737, the planemaker’s largest source of profit, and an unexpectedly large one-time gain from US tax cuts.

The tax reduction is taking effect just as the company starts to see large, taxable cash gains from its 787 Dreamliner after a decade of losses.

Lower taxes are combining with record jetliner deliveries to fuel the cash gush at Boeing, the biggest gainer on the Dow Jones Industrial Average last year and so far in 2018. Free cash flow was $2.47 billion in the fourth quarter, Boeing said in an earnings report Wednesday, exceeding the $1.66 billion expected by analysts.

“The buy-back and cash flow have been the whole story on the stock for the last year,” Ken Herbert, an analyst at Canaccord Genuity, said in an interview before earnings.

Shares climbed 4.1 per cent to $351.50 before the start of regular trading in New York. Boeing had advanced 15 per cent this year through Tuesday, the largest gain among the 30 members of the Dow Jones Industrial Average. The stock has more than doubled since the start of 2017 as Boeing surpassed General Electric Co. to become the largest US industrial company by market value.

Revenue has declined since 2015. Boeing slowed deliveries of its highly profitable 777 jetliners as sales waned amid a shift to a new model. But earnings per share have continued to rise, boosted in part as buy-backs contributed to a 15 per cent drop in the company’s average share count.

Under Chief Executive Officer Dennis Muilenburg, Boeing has rolled out new planes like the 737 Max and 787-10 with few glitches while rival Airbus SE battled engine delays for its A320neo and A330neo. Muilenburg’s campaign to make Boeing leaner has lowered the cost of goods and services.

The plane maker is forecasting sales growth in 2018 as Boeing lifts 737 output by 11 per cent and pockets additional tax savings. Revenue will range from $96 billion to $98 billion, the company predicted, compared with the $93.6 billion expected by analysts.