pdcta,
From a pilots point of view that's not always possible:-
1. The AO files the plan and requested level several hours ahead of STD. This is based on computer predictions of planned weights and minimum fuel loadings.
2. The above calculations are just that - 'Predictions' - the actual aircraft weight at departure can preclude climb straight to FPL as it's easier to be heavier, and therefore not capable. Payload prediction can change. Additional fuel carried over and above legal minima can occur on many occasions because the crew have valid reasons for loading more.
3. The tactical situation I.M.H.O is far more variable than your 'stick rigidly to everything in the filed FPL' sentiment suggests:- CTOT's mean being airborne within a 15 minute window of the FPL time, so the ACTUAL presentation and appearance of traffic to a sector is still VERY variable, based on just initial FPL data. This HAS to effect the decision making process that an individual controller HAS to make to allow safe and efficient controlling.
4. I very much appreciate sectorisation, and capacity issues that occur when at different to FPL. I couldn't possibly count the times I have been filed and flown at say FL340, then been asked if I could accept FL360. Having accepted, because it HELPS the resolution of a problem for the controller concerned, I have then been transferred at new FL continually en-route at that higher level, including into airspace we have tactically filed under at FL340 in the first place for capacity issues.
What I do believe is that ATC must be left to BEST manage the tactical picture at the time. Pilots should NOT abuse capacity planning by REQUESTING levels that would infringe tactical level planning to avoid CFMU restriction.
Brgds
30W