Hey planefags, thanks for all the updates in the main breads. I have some basic questions if you have the time.

1. What procedure is in place to achieve the blocked call-sign status? Where does the authority to have that status originate and it is just for public info radar or can the commerical/miltary radar have the correct call sign at any given moment? Or, is it up to the pilot throwing a switch?

2. I see a lot of no call-sign status, particularly for smaller aircraft. Is this normal and how is that come about as well?

3. I notice most most commercial airliners travel at about 507 knots. Is that near top speed or just the sweet spot for fuel consumption?

Thanks in advance. Keep up the good work.

Question: A plane flies over your house and it does not show up on any of the flight tracker sites AND isn't military. What can you assume or infer from these facts about the plane?