As we all know, there are many collective nouns in the English language. Some are well known such as “a herd of cows” or “a school of dolphins“. However there are many more “exotic” ones : did you know that “a gaggle of geese” on the water become “a skein of geese” in the air ? Were you aware it is “a murder of crows“, “a skulk of foxes” or “a murmuration of starlings” ?
Most of these date back to a famous printed work The Book of St. Albans of 1486. In this, many of these colourful if unjustifiable rules were set down.
However more common phrases such as “A flight of stairs” are not from this source and merely developments of the language over time. As a flight is generally accepted to be a single, straight set of steps from one landing to another it is possible to see how a word such as “flight” might come to be applicable but it is not possible to track an etymology for this phrase.