I'm a dispatcher for a regional airline.A captain on one of my flights asked why he was filed at FL310 for the west bound flight, he also said that was the third that had happened. I checked the flight strip that was sent to ATC it had FL340 on it.
After re-reading this situation, this was almost certainly to fulfill a requirement spelled out in a Letter of Agreement between SLC Center (or Approach) and SLC tower. Clearance delivery is probably required to make sure flights going out that way are expecting odd altitudes. After departure, the radar controllers responsible for actually dealing with the flight can make the determination (either themselves or via verbal coordination with the facility requiring the altitude) to change the cruising altitude back to whatever the pilot wanted.
That's interesting! Does center fix routes, or do you?
We do. We need to make sure routes comply with Letters of Agreement, same with the altitudes requested. It's all spelled out in writing, though some of it may be done automatically by our flight data computer. Say we get the following route for EGF3263 and it is:
"KACT KDFW" (otherwise known as "direct")
When we get the flight plan strip printout, it will look like this:
+JEN JEN9+
KACT KDFW
And we'll clear that flight "via direct Glen Rose, Glen Rose 9 arrival." The altitudes don't get changed automatically like that, but since we have to memorize all LoAs with adjacent facilities, we'll know when an altitude needs to be amended. At that point, it becomes like you say here:
Some leave the requested in until they are talking to the plane then work it out with the pilot, others change it on the ground then tell the pilot when they check in, and others change it on the ground and don't say a word to the pilot unless questioned.
Different techniques, for different folks. I always prefer to change it immediately to comply with our agreements, so if the next controller sitting down doesn't notice it, we don't have a goof. After issuing the revised altitude, I expect the pilot to speak up if they have an issue with the new altitude (it's usually only different by 1,000 ft or so).
At my center, we have to check all the routes that will enter our airspace, and either put any change in the computer or, if it's within 15 minutes of the p-time, call the tower/approach that will give the clearance so they know a revision's coming.
This sounds similar to what we do, but it mostly comes through the flight data computer automatically. At towers without a flight data computer, I could see the need for those procedures. If we don't get an automatic amendment to make the route "legal" we're expected to know to make the proper amendment ourselves, because we have the agreements memorized. Since the LoAs cover how aircraft are allowed to exit our airspace, it really doesn't matter how far in advance the amendment occurs. It mostly all gets done well before the aircraft even picks up their clearance, much less departs.
Interestingly, out flight data computer only "plus routes" (places routing between plus mark symbols) for portions of the route into the next facility or two's airspace. Beyond that it usually goes "direct" to the destination airport. Since everything is connected, I don't know why the routing isn't just calculated out as far as possible, but I expect pilots get caught off guard when the departure tower clears them "direct," or with a small route change THEN direct, and shortly after departure Center completely re-routes them.