WASHINGTON (MarketWatch) - Orders for big-ticket U.S. goods jumped 4.2% in July as demand for airlines and autos surged, but bookings weakened in many other sectors, the Commerce Department said Friday. Economists surveyed by MarketWatch had expected orders for durable goods to climb 3.0%. Bookings for transportation equipment, a particularly volatile category, shot up 14.1% last month, as Boeing received its biggest batch of orders since last December. Yet omitting the transportation sector, orders fell 0.4% and declined for the second month in a row. Orders for core capital goods excluding defense and transportation, a key barometer of U.S. business spending, dropped a sharp 3.4% last month. These orders also fell 2.7% in June.