I once borrowed a bag from a friend for a trip to the US. When asked by the additional security at MAN before getting to check in, I answered truthfully that it wasn't my bag and got a bit of the 3rd degree.
However, when I explained that the person I'd borrowed it from was a senior officer in the anti-terrorism branch of Greater Manchester Police, and could provide contact details etc., he calmed down.
The bag would still have been x-rayed, as all hold luggage is nowadays.