a craft resembling a large blimp appears out of thin air from a cloudless sky ,descends, lands and vanishes

My brother and I were traveling eastbound on state hwy 3 approximately 4-5 mi west of Humboldt, Ia. The sky was clear and there was not any other traffic. I was returning him home to our parents as he was 13 or 14 years old. He had been visiting me in the western part of the state. We were talking as I drove along and as if out of a science-fiction movie a large craft just appeared above and to the left of the road about 1-2 miles in front of us. I mean, I was looking ahead when this large craft just appears in the sky. It was descending abd was tilted down at about a 45 degree angle.
 It then leveled itself over the highway then descended again, tilted down as before, and left my sight as there was a farm building sight with a grove of trees blocking my sight. That's when I turned to my brother and found him looking at me. At the same time we both said "Did you see that?". We're still traveling east and getting closer to where we saw this thing land. I say 'land' because we're in Iowa and we can see the farm place and all around the vicinity for a long way. I mean, we were really wondering what this was going to look like on the ground and close enough to the road to throw a rock and be able to hit it, to make a point. Probably a minute after we lost it from sight we were passing the farm place and there was'nt anything there except a harvested bean field. We arrived at our parents house a couple of hrs. later and told them about what we had seen. Understand, it's been 33-34 years since this took place, but our oldest sister[17 at the time] it was either 1 or 2weeks later brought my attention to the Des Moines Sunday Register. On the front page the second bold -type heading read" Mysterious burn spots found in soybean fields " and went on to mention Iowa and surrounding states south and west of Iowa. My brother would not talk about this at all for maybe 23-24 years later. I don't have an explanation concerning what we saw that morning, but everytime I hear or see the word"stealth" I tend to shake my head a little. I'd like to see our military make something the size and shape of the Goodyear blimp just "appear out of thin air and then "vanish" into thin air. This report is as credible as our Earth orbiting the sun.