Boeing (BA), the world's biggest maker of aircraft and spacecraft, raised its forecast for sales of its flagship 737 jetliner, based on significant growth in orders for single-aisle jets. The aerospace giant is currently making 35 of its 737 jets a month, and expects to see that number rise at a faster rate than its current forecast for 38 jets a month by the second quarter of 2013 and 42 a month in Q2 '14. Boeing's planned 737 MAX line will be