Maybe you saw something different at the time you checked, but I checked just now, and all Chicago to Seattle flights at any time on July 6, 7 and 8 (Fri, Sat, Sun) are 20K miles per ticket, one way.

When I talked with the Alaska desk about the July 6 LHR option, they did not say I could overnight in Chicago and then fly out on July 7 or July 8. I had inquired about this on a previous day and the reps had said it would need to be a separate ticket, at 20K each, if no saver seats were available. This seemed to be the situation for the July 6 option of going LHR to ORD. But yes in hindsight I could have double checked about the availability of the ugly routing on July 7 instead of on July 6. I think it would have had to be within 24 hours anyways, which might or might not have been available. Anyways, water under the bridge at this point.

You're right that the scenario does not prove Alaska's and American's award seat availability is different. I guess the 'proof' is different reps saying the same thing over and over. For example, I called Am Air yesterday and specifically asked about Paris to Boston on July 7. They said "we have 3 seats." I called Alaska and asked about the same flight. They said "we have 1 seat." Alaska does not have access to all the seats American has. And neither of them were then able to put together a routing that would get us from Boston to Seattle on that day or a day later (July 8). it is too bad because layover in boston would be great.

Nearly all of Alaska's seats going to Seattle from anywhere beyond a 2 hour flight (namely San Francisco area) appear to be 20K one way, even 11 months out. According to the reps I've talked with, this pretty much blows out of the water the availability of saver awards using Alaska, which is the point I'm trying to make to future readers who might be considering where to gather miles for the best chance of award travel in the future. However, this could change and is definitely worth checking in the future. Or maybe it even varies today depending on which rep the caller talks with? Or depending on how many layover there are and time of the day (eg, someone willing to fly from a city to another city to another city to another cite may be able to get a lower price award).

Maybe others will be luckier than I have been. But, they should definitely check the calendar to see what the levels are. This is the mistake I made.

Examples:

Seattle to Chicago - 20K one way starts May 6, 2012 through Aug 14 (with the last day posted, Aug 15, having an even worse 27.5K miles one way).

Chicago to Seattle - 20K one way starts May 17 and goes for all flights listed thru Aug 14, with Aug 15 also 27.5K miles.

Even April and May, the only 12.5K seats are on Tues, Weds and some Saturdays.

Seattle to Burbank in July 2012 - I found that on Tuesdays there are seats at 12.5, other days they all seem to be 20K. LAX and SAN were all 20K. SJC was 12.5K.

Good luck with your future bookings!