I was walking Sweeney Ridge trail today, sunny blue skies with huge cumulus clouds after morning rain. While admiring the clouds I noticed what appeared to be a stationary, thin, short, dark line at an angle leaning to the right, not unlike the backslash on a typewriter/computer keyboard. It seemed quite far above, higher than the air traffic/planes commonly seen flying along the pacific coast. While watching the object and trying to figure out what it was, 2 more appeared close by and sidled up alongside the first, all at the same angle. After some minutes, they suddenly were no longer to be seen. The incident lasted about 15 minutes. I continued my hike, frequently scanning the shy, but saw no other air born irregularities :)