* CSL-only, in which JEIM is done at a CSL in both peace and war (CSL).
When engines accumulate enough flying hours or when unscheduled maintenance is required, they are removed from the planes and sent to a JEIM facility.
Once parts and labor are available, JEIM personnel repair the engines.
Resources needed to give equal performance, as measured by missed sorties, are used to compare JEIM alternatives.
The reason for the decline in serviceable spares up to day 60 (negative spares means that engines are not available for all aircraft) occurs because, under the current repair structure, JEIM personnel deploy to an FOL by day 30 of the war and begin work immediately.
Deploying more rail teams cannot solve this problem since there are too few WREs for the period when the deployed JEIM is not operating.
For the decentralized no-deployment structure (home support), the JEIM remains at the home base and supports deployed forces from there.
In this structure, a JEIM shop is located at an FSL in theater and supports engaged forces.
An alternative FSL arrangement is the CSL-FSL structure with some CSL staff performing peacetime JEIM and some deploying to an FSL during war.
For the deployed JEIM scenario, as many as 12 F-16s and 22 F15s can be without serviceable engines.
Those with less centralization develop a large backlog of engines during MTWs and, hence, a dangerously low level of spares before a deployed JEIM can begin repairs.
The latest Air Force unit type code (UTC) list describes several different F-15 and F-16 independeOnt (that is, capable of operating by themselves) JEIM UTCs ranging in weight from 25 to 50 short tons.