The grandstands are filling now as the Czech-made L-39s drop into the course on their run to the first pylon. The jets are a new class at Reno; as all are virtually identical machines there is some close racing at speeds nearly as high as the Unlimited Gold racers. But they don't make that glorious full-throated rumble characteristic of a big radial engine or the special, complex sound of a V-12 Merlin at full power; the response from this crowd is pretty much ho-hum.