I have noticed that in the Star Alliance availability of UA award seats may be different for Mileage Plus members than for Air Canada's Aeroplan members. Does anyone know if the availability of award space is different for a given seat on a one world carrier based on which program the member belongs to? IOW if a seat on AA is unavailable to an Executive Club member will it be unavailable to an Aadvantage or Asia Miles member?

Welcome to FT, flyingmd817!

In general, within *A the availability is the same. The exception is UA which blocks some awards for their members. This is usually referred to as the StarNet blocking. There are other exceptions within *A as well like awards for SQ premium cabins which are mostly available on SQ and M&M.

For oneworld, the theory is the same. All awards are available for everyone. However while there is no StarNet blocking there are still certain differences.
For example QF is opening awards for their members 355 days before the date. The rest of oneworld only gets access 330 days before. So potentially some key routes will have been taken before other programs even get a chance.
LA is an airline which frequently only makes awards available to their own Frequent Flyer. I often had the problem that I could not book their flights using QF points but had to use LA km to get a seat.

And last but not least, many airlines (not just OW) will make award seats available only for their own frequent flyers upon request. So even if there is no award seat available, QF will make one for me if I request it and the flight is not too full.

I am not meaning anything negative about you in the post. I am actually glad there are some ppl who noticed UA's extra blocking by themselves. I was one of those ppl who were fooled by UA thinking that its partners were not releasing seats. I came to know of this blocking only through FT. It frustrated so much that I now have stopped accruing in UA unless there was an opportunity to accrue only in UA.