In another sign of an economic recovery of some measure within business aviation, Cessna confirmed it plans to add 400 workers to its current Wichita employment level of 8,100. An increase in scheduled bizjet deliveries this year and next, along with the introduction of new Citation models, prompted the hiring, a Cessna official said. It wasn’t immediately known how many of the 400 hires Cessna might recall from the more than 3,300 jobs cut since late 2002. In the first quarter, business aircraft manufacturers delivered 144 turbine airplanes, 21 percent more than during the first quarter last year.