Airplane flying from horizon to horizon

[Quiznite]

OKay here goes'

If i was stood on salt flat or desert and could see an airplane leave a vapour trail that went from 1 horizon to the other and the plane was 30'000 feet high .

How long would the vapour trail be ?

I

[kempie]

How tall are you?

[mibn2cweus]

Assuming an elevation of sea level, perfect visibility and ignoring refraction over the horizon, negating atmospheric effects:
Using the Pythagorean theorem the radius of the Earth at sea level is about 21 million feet (20 925 646).
21 000 000 squared equals 441 000 000 000 000.
21 030 000 squared equals 442 000 000 000 000.
Square root of difference equals 1 million ft.
For both directions assuming overhead flight the distance works out to
2 241 819 . 6 feet or about 425 miles (683 km).

Although refraction of the atmosphere extends visibility "below" the horizon, visibility rarely exceeds 100 miles.

See alternative calculation at bottom of this page