UFO's are Unidentified Flying Objects.
Once they are identified they become IFO's (Identified Flying Objects)

There are no alien spacecraft..

The first posters claims about early RADAR picking up UFOs shows that
his education on the subject has serious flaws.
One of the major problems of the early RADAR is now a major part of
every weather avoidance system.
CuNim clouds have vertical currents that can destroy aircraft.
These CuNims can be detected on RADAR by the water content of the
cloud and thus avoided.
However RADAR is unable to detect CAT (Clear Air Turbulence) because
there is no water content.
When RADAR was first used at sea the 'background' scatter of waves
caused many problems.

All this is nothing new and crazier posters have attempted to make the
same claims over the years.
In the years that I have followed the subject many claims as to how
the 'government' was going to admit alien visitation 'next year' and
how some-one had an 'alien implant' .
And the claims that the 'government' has 'Flying Saucers/Alien Flying
Vehicles' hidden away somewhere on some military establishment.
Yet in all the years these claims have been made no-one who has served
on these Bases has ever been found who 'knows' of these places.
In the military the squaddie sweeps out -all-the buildings on the
Base.
And I repeat:
Some-one must be guarding those sites, painting them, cleaning them,
replacing lightbulbs and so on.
The ranks need feeding, housing, married quarters, pay, sickbays,
transport, supervising officers.
You cannot hide all these people from the ordinary daily routines of O
R on the Base..