No - I can guarantee they were that close.
It was obvious that this was on purpose.
Maybe not 30 feet, but less than 100.
They flew directly over me while I was waitin at a stoplight just
southwest of the airport.
The small jet was probably about 50 feet back, no more than 100
feet away. They flew directly next to each other turning east.
Afte getting some perspective, the small plane was probably also down about
50 feet from the MD-80.
This was no mistake.

I watched them for more about 2 minutes.

The small plane had to be some sort of escort to the large plane.

I'm telling you, this was tight formation flying, no accident.
How they took off - I don't know. I didn't get to see them until they
were at about 1000 agl or so.

Given that I've flown about 20 hours, and watch planes
frequently at the local airport, I am that sure they were in formation
flight. The small plane was matching the flight of the large plane.
Again, they turned together, toward the east. I might have believed it was
something else, but for about 2 minutes of watching.

I wonder if it was an NSA plane (staff or something), or another agency
flight.