What altitude is that plane at?

[searchlight]

Looking up at a commercial aircraft is it possible to estimate its altitude to a reasonable degree of accuracy by sight alone?

[lord molly]

yeah, with in several hundred feet prehaps
a got give away is the size at which it appears and weather or not it is co-trailing, whch usually occurs around 15-20 feet depening on temp and pressure

[lord molly]

make that 15-20 thosand feet