Boeing Co's Sonic Cruiser, a proposed faster airliner, would be mostly blended material, p

rogram director Walt Gillette said recently. In its quest for the 【21】______ to fly 15 to 20 per cent faster than 【22】______ airliners, the US company says about 60 per cent of the new plane's 【23】______ , including the wing, would be a carbon-fiber-reinforced composite material that is lighter than aluminum for the same 【24】______ . "Composites would 【25】______ almost all of the airplane that you could see from the outside," Gillette said. Composites are well regarded among aeronautical engineers and have been in 【26】______ use since the 1970s. Each generation of planes has more composites, and Gillette 【27】______ that about 10 per cent of Boeing's 【28】______ civil aircraft, the early-1990s 777, is built 【29】______ the material. 【30】______ still only a proposal, the Sonic Cruiser has 【31】______ the interest of many airlines, which expressed unusual enthusiasm for the aircraft 【32】______ the September 11 attacks forced most of them to scale back operations. When Boeing 【33】______ the Sonic Cruiser last year it said the plane might enter service 【34】______ 2006 and 2008. Gillette said the 【35】______ date now is 2008, by which time the market and technology are expected to have developed 【36】______ Wind-tunnel tests 【37】______ the company's computer calculations of optimal cruising speed for the plane at 95 to 98 per. cent of the speed of sound. Going faster than sound would use too much fuel and 【38】______ great 【39】______ on the aircraft's engines. Gillette said the Sonic Cruiser 【40】______ be offered as a family of aircraft with 200 to 250 seats and a range of 6,500 to 9,000 nautical miles (12,000 to 16,700 kilometers).

【21】

A．proficiency

B．efficiency

C．affection

D．effective