Complex sentence: Miles in a member's account can be exchanged for award flights on all the fully integrated airline partners and all of the Star Alliad flights are subject to availability and are not available on all routes on all dates.
Split into simpler sentences: Miles in a member's account can be exchanged for award flights on all the fully integrated airline partners and all of the Star Alliance carriers. Customers do, however, have to take into account that these award flights are subject to availability and are not available on all routes on all dates.