Indeed they would be jettisoned only if doing so would be critical to either
the mission of the survival of the aircraft.
The situation you mention is one, another is where the pylon itself is
heavily damaged causing a lot of drag which would prevent the aircraft from
reaching home.

Or you might think of an F-22 carrying external fuel to penetrate into enemy
territory jettisoning those tank and pylons to decrease its radar cross
section for the commencement of the combat part of its mission (and meeting
a tanker on the way out).

"Jeremy Thomson" wrote in message
m...
In my 'Great Planes' video of the Northrup F5 Freedom Fighter it
talked of the 'Scochi Tiger's being brought up to USAF standard with
among other things 'Jettisonable Pylons'.
I guess that meant the pylons with which the bombs, rockets & fuel
tanks were attached.
I suppose if an aircraft had taken a hit in a fuel tank & you
absolutely must wring out every last bit of range to get you out of
indian country, jettisoning the pylons would save a little weight &
drag.

Under what conditions would plyons be jettisoned?
I dont know but is it usual these days for fighters to return to base
keeping their empty drop tanks with them?
Are plyons still jettisonable as USAF standard?

Jeremy Thomson