Britain's Rolls-Royce said on Tuesday its Trent 1000 plane engine had received its airworthiness certification, clearing the way for the first flight of Boeing Co.'s hot-selling 787 Dreamliner.

The Trent 1000 continues to set the pace on the 787 program - first engine to run and first to be certified, Mike Terrett, president of civil aerospace at Rolls-Royce, said in a statement.

Including business yet to be announced, orders have been placed for over 500 Trent 1000 engines by 15 operators and five leasing companies - approximately half the Boeing 787 customers, the company said.

GE Aviation has also developed an engine for the 787, which is the fastest selling airliner in Boeing history.

On a date symbolizing the plane's name -- the seventh day of the eighth month of 2007 -- officials from the European Aviation Safety Agency (EASA) handed over the airworthiness certificate.

A spokesman said the U.S. Federal Aviation Administration (FAA) also certified the engine on Tuesday.

The twin-engined 787, which is scheduled to enter service next year with Japan's All Nippon Airways, has won 684 orders to date, according to the planemaker's Web site.

Boeing Chief Executive Jim McNerney told analysts on a conference call last month that the 787's first flight had slipped to the latter part of its target of late August to late September.

We are at the back end of the window right now, said McNerney, adding that Boeing had contingency plans to get back on track in case the first flight slips into October.

Boeing rolled out the first 787 from its plant in Everett, Washington, last month.

Rolls-Royce shares were up 0.4 percent 502-1/2 pence as of 1420 GMT versus London's FTSE 100 which was up 1.19 percent.