Did the pilots encountered some type of weather instrument tied to the ground and sailing dangerously above? With the size described, it would be an exceptionally large box kite. Most that carried instruments at the time weren't much larger than a wardrobe. And how could two separate pilots--one of whom was an experienced racer--have missed that there would be a kite unfurled to 1,000 feet in their flight path?
And what of the description of it being a 'monster'? Is that journalistic hyperbole designed to sell? The pilots themselves described it as a 'contraption', so they knew it was a machine and not a monster.
Was this an early report of a UFO? Or could it have been a dangerous case of mistaken identity by two experience pilots?