WT
Adjusted CASM is merely a mathamatical forumula that takes into account the stage length and unadjusted CASM. So in the case of UA and DL. DL's June CASM should be 6.5 divided by the 7.64 for UA. That figure, times DL's LOH 1152 divided by 1700 miles. Plotted on a graph this would be a straight line so it's not a real world scenario.
In the real world, adjusted CASM is a curved line that drops steeply in the shorter LOH range and levels out for longer LOHs beyond 900 miles. This is due to fix costs being spread out over more miles at first, but in longer LOHs fixed cost are not a big factor anymore and you still left with fuel, and employee costs.
So DL's 58% adjusted CASM in comparison to UA is just rough guide. In the real world it's not that bad.
Artie-
Actually, I'm going to have to disagree with that analysis. A rough guide of a 42% advanatage isn't even close, especially now that I've finally found some curves I was looking for. I couldn't find them last night when I posted.
These are the numbers I have. As I posted above, UAL's mainline/consolidated CASM (including fuel) was around 11.43/12.11 for 1Q06, the earliest "full quarter" of data I can find for DAL. DAL's CASM (including fuel) was around 11.12/12.15 respective to UAL's for 1Q06. The nearest data I can find concerning stage lengths is that back in 11/05 DAL had an average stage length of around 1020nm. UAL's is around 1350nm. I'll come back to this later.
As an interesting aside, WT you often claim that DAL is making dramatic changes in the bankruptcy process. You write that no other airline used this time to lower their costs better than Delta has. Well, if we're looking at just the raw costs above, I'm not buying it yet. According to each airlines' 2000 annual report, DAL had a CASM of 9.68 and UAL had a CASM of 10.63, for an advantage of around 9.1% in DAL's favor. DAL has historically enjoyed lower costs than UAL, and if one takes into account the longer stage length UAL probably had during that time (that disparity was probably greater back then then it is now), the cost advantage in DAL's favor widens further. So WT, in order for me to believe that DAL is doing a dramatic job cutting its costs, far better than UAL as you claim, I would expect DAL to WIDEN that 9% CASM gap during the current bankruptcy process (compared to the 2000 numbers), especially stage length adjusted. If all DAL can do in the bankruptcy process is "approximate" UAL's costs as it currently is doing according to its latest full quarterly report, I would argue that DAL is not doing a good job cutting its costs at all. In fact, one might even argue that UAL did a better job. I do realize, however, that DAL is incurring costs in the bankruptcy process that it wouldn't otherwise, so I'll admit that using that 1Q06 data might not be a fair comparison.........yet.
Back to stage length adjusted data. Artie is right in describing the stage length adjustment when looking at a curve. If you can imagine a graph of y=1/x^2 - the slope of the curve is very steep on the "left" hand side of the curve and flattens out considerably as one looks toward the "right" side of the curve. If you looked at a curve for stage length adjusted CASM for an airline, the curve would look sort of similar.
That's why the linear interpretation that Artie made concerning UAL's vs. DAL's cost isn't even close. I'm a big fan of "back of the envelope" computations simply because I don't have the accurate data that the professionals of the world have and taking an airline's CASM out to 5 decimal places doesn't make sense. But Artie's rough numbers are way off in my opinion.
When you look at a curve for adjusted stage length curves, the curve is considerably flatter the longer the stage length is. That's because you're spreading the high costs of taking off and landing over more seat miles, so as an airlines' stage length increases, the "adjustment" made becomes smaller. In fact, in the DAL and UAL case I would argue that adjustment using the numbers in the 1st paragraph is in the neighborhood of a few percentage points (i.e. certainly less than 5%). And I imagine with DAL's recent rapid expansion in Europe that the stage length data for DAL has actually increased, further lowering that adjustment when comparing the two airlines.