Aviation professionals, high school teachers, politicians and pilots were on hand for a very special “airmail” delivery in the capital city. A military transport copter with two gigantic rotors dwarfed the Huey helicopter carried in a sling below it, as the craft came in to land at Des Moines international airport Wednesday afternoon. Students at Des Moines Central Campus tech school will have an opportunity any high schooler would envy: to work on a real working chopper, of the kind pilots flew in Vietnam.