spares back up

Hi,

Not sure where to post this as it applies to all aircraft.

When aircraft are ordered and put into production what are the spares back up?

For example 40 Javelin F(AW) Mk1s were ordered in July 1952. They were delivered between Oct ’54 and March ’56 and started to enter service in Feb ’56.
So 40 aircraft were ordered but what about spares? How many spares would be ordered? Parts had to be replaced on a regular basis so there had to be a replacement service set up.

Any ideas? This would apply to any aircraft of course.

Alex