Radars receivers and tracking software operate by performing hypothesis testing on return signals. The set of hypotheses they accept do not include the kind of fantastic targets described. Real targets of interest are constrained by aerodynamics. Radars will not track meteors for this reason. Accounts of interaction between air traffic control (ATC) radar operators and SR-71's are manifestly apocryphal. ATC radar won't track targets moving at 4000 kt.
Pilots may be visually associating unrelated returns from airborne corner reflectors, radar artifacts (e.g., second time around returns) or migrating waterfowl, or any one of a thousand other things. Especially considering these are new radar sets, these reports provide very weak support for extraordinary claims.
“Accounts of interaction between air traffic control (ATC) radar operators and SR-71’s are manifestly apocryphal. ATC radar won’t track targets moving at 4000 kt.”
Mach 3 is 2000 knots