Following last year’s tragedy and new recommendations by the National Transportation Safety Board and Federal Aviation Administration, the Reno National Championship Air Races are set to begin Thursday with four days of competition and a full-spectrum air show. Pilots of six racing classes gathered at Reno/Stead Airport Saturday to meet new requirements, including expanded technical inspections of aircraft, briefing of course changes and rules as well as proficiency training prior to qualifying runs that began on Monday. Enrollment in all categories is nearly full with a total of 109 airplanes, ranging from 150-mph biplanes to the fastest jets, reaching well …