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that visibility was expected to be three miles.
During the descent and approach to LaGuardia an observation was taken that showed the first definite deterioration of weather and was as follows: ceiling measured 1,700, broken, with an overcast at 2,800, visibility 1½, very light rain and smoke, wind ENE 4. This was given to the flight at 0900. Following this the visibility at LaGuardia dropped to one-half mile at 0909 (six minutes after the accident), and the ceiling was reported to be 600 feet at 0910 because a low broken stratus layer moved over the field. However, at Idlewild, the alternate, the ceiling did not drop below 2,700 feet, nor visibility below one mile, up to and including 0923.
A very low layer of stratus coupled with poor surface visibility lay north of LaGuardia at the time of the approach of Flight 801 and possibly before that time. However, weather reporting stations were unaware of this condition, and its presence had not been reported by any pilot. Surface and low altitude wind at LaGuardia had been light southeasterly but shifted to ENE at 0900 and to E by 0910, causing this low stratus to drift across the airport. It is possible that a continuous watch by a weather observer might have revealed the moving in of the low clouds a little sooner than was reported, but probably not in time to have given it to the flight. This condition of surface weather at the time and place of the crash is well substantiated by passengers, both pilots, and rescue personnel. Their testimony indicates that there was a horizontal surface visibility of one-half mile or less with no wind, resulting in an unusually smooth (glassy) water surface. Pilot reports from flights operating at LaGuardia shortly after the accident confirm rapid fluctuation of weather conditions. One flight approaching the same runway
