In article , Gary G
wrote:

I drive to work just south of BWI/Marshall airport every morning. I
looked up and literally thought there was going to be a mid-air
collision!
What I saw was a plane that was along the lines of an MD-80,
and off the right wing was a corporate jet - something around an
8 or 10 seat - corporate jet. It was about in the range of 30 to 50 feet
off the wing.

I can guarantee they were farther apart than 30 feet -- that's less
than the wingspan of the smaller jet!

My guess is that the corporate jet took off of runway 15L, and the
MD-80 used 15R. They're parallel runways, and they're both in use at
the same time. The guy using the left-hand runway will either go
straight out or make a left turn shortly after departure; the guy on
the right, just the opposite.

The runways are separated laterally by about 4800 feet, and I doubt the
planes got much closer than that once they were airborne. They just
*looked* closer due to their large size.