Originally Posted by
WhyNotKnow
The holding pens are removed when the AITs are install since there isn't room for both. The holding pens are primarily used with the WTMDs for passengers who alarm so there is a positive hand off. Without them the WTMD Officer would have to stop the line to pass off the passenger for secondary screening. They are used to prevent breaches which cost not only airlines but passengers money.
Airports around the world manage this without glass "holding pens". I've set off the WTMD (due to a hip implant) in SYD, MEL, CBR, AKL, NRT, HKG, SIN, ZRH, GVA, FCO (...) and
NOT
ONE
OF
THEM
put me in a glass booth so I couldn't "escape" while waiting for my patdown.
NOT ONE.
In every single case*, the WTMD person said, "Just stand here", motioned to one side, called for someone to either do the patdown or to take over WTMD so she could do the patdown, and just got on with it. No silly mat with footprints, no waiting 5, 10, 30 minutes. If Australia, NZ, Europe and Asia can all handle this,
what the he|| is wrong with the USA? (Don't answer that, we don't have time for the full list.

)
*I tell a lie. In NRT, the apologetic young lady gave me a
chair where I remained while she ran my shoes through the WTMD, got my patdown
and put my shoes back on.