Paco. Materiel and provisioning support polices (because that is what we're talking about) have changed innumerable times since Tornado entered service. I doubt if anyone could even describe a few of the changes. But I remember one, in April 1990. Hitherto, RAF suppliers had run a max/min stock level system, the aim being to satisfy demands from units within the timescales set out in the FUD system. (From memory, Priority 1 - 24 hours. Priority 2/3/4 - 48 hours. And so on). Plainly, this required stock on the shelf, based at first on predicted reliability, then fine-tuned with experience. The likes of engines were easy to calculate, because one didn't let them fail before taking them out for overhaul.
In 1990 this policy changed overnight to only initiating procurement when there was an outstanding demand. In other words, a Not In Time policy. The delivery forecast was the production lead time, which was many months or even years. Later, this was improved by the much-maligned Just In Time policy, most people not realising this was a major victory over beancounters, by those who wanted aircraft flying. JIT was actually a minor tweak of the old system NIT had replaced.