J. Allen Hynek:
Air Force Unidentified: April 24, 1949, Las Cruces, New Mexico. Time: 10:35 A.M. Since this case was described to me personally by the chief witness, Charles Moore, in charge of a special Sky Hook balloon project at White Sands, New Mexico, my files on it are more complete, more detailed than Blue Book’s. The actual story follows: 

On a bright sunny New Mexico morning, a small balloon was launched to test the winds aloft preparatory to the main experiment. Such small balloons are customarily watched through a theodolite, a small telescope that pivots in two directions to give accurate sighting angles. Moore watched the balloon as it ascended higher and higher, and then, having another duty to attend to, turned the instrument over to one of the Navy men on the team, admonishing him not to lose track of the balloon. Glancing back a few minutes later, he was shocked to see the Navy observer pointing his telescope elsewhere in the sky than where Moore could see the balloon with his unaided eye. He descended upon the unsuspecting observer and dressed him down severely for having lost the balloon. 

“But, I’ve got it right here!” the man exclaimed. 
Sure enough, he did have an object in his field — an elliptical object, two and one-half times longer than wide, moving rapidly enough to require skill in following it through the telescope. Moore grabbed the telescope and confirmed the sighting. Then he called it to the attention of the rest of the crew, all of whom had no difficulty in visually spotting the object. The precious balloon was forgotten. All eyes were on the unknown object. As the crew watched, the object suddenly stopped its horizontal motion and climbed very rapidly, vertically, and was soon lost to both telescope and eyesight. 

There could hardly have been better qualified observers. The desert was still that morning. There was no manmade noise. Yet, neither Moore nor his crew heard any sound from the unknown Daylight Disc! 

Moore was disgusted with the Air Force’s and my lack of attention to this sighting. Who can blame him? It was typical of the Air Force’s practice of spending a great deal of overkill effort pinning down cases for which there seemed to be an immediate logical explanation in sight and devoting only modest follow-up to a case that was truly baffling. The Air Force, however, did finally label this case unidentified. 

J.Allen Hynek
Source: The Hynek UFO Report, by J. Allen Hynek, (N.Y.: Dell Books, 1977) pp.104-105.