UPDATE 2-Boeing forecasts sharp rise in profit, jet output in 2018

(Rewrites, adds forecast)

NEW YORK, Jan 31 (Reuters) - Boeing Co on Wednesday forecast full-year profit well above Wall Street estimates as it expects its busiest year ever for plane deliveries, sending its shares up more than 5 percent in pre-market trading.

The world's biggest planemaker said it aims to ship between 810 and 815 commercial aircraft in 2018, as much as 6.8 percent more than the industry-record 763 jets it delivered in 2017, putting it ahead of European rival Airbus.

Helped by the strong demand for jets, Boeing forecast core profit would rise to $13.80 to $14.00 a share in 2018, ahead of analysts' average estimate of $11.96, according to Thomson Reuters I/B/E/S.

For the fourth quarter ended Dec. 31, Boeing's core earnings nearly doubled to $4.80 per share from $2.47 a year earlier, buoyed by rising plane output and a gain from changes to the U.S. tax law.

It booked a one-time tax gain of $1.74 a share due to the lower U.S. corporate tax rate signed into law last month reducing its deferred tax liabilities in the future.

Excluding the gain, Boeing reported earnings of $3.06 a share. On that basis, Wall Street had been expecting $2.89 a share.

Boeing forecast that operating cash flow, a key measure of its financial performance, will rise to about $15 billion in 2018, compared with $13.34 billion last year. (Reporting by Alwyn Scott in New York and Ankit Ajmera in Bengaluru; Editing by Saumyadeb Chakrabarty and Bill Rigby)