US Airways, American Airlines, and British Airways are all members of the oneworld alliance who should be equally sharing award space on their own flights with their partners.

For the first time, I've found a case where US Airways "Low" (their name for "Saver") price award space is not bookable with American Airlines or British Airways miles.

Either the US Airways space is phantom, or it isn't being shared with American Airlines and British Airways, which would be a huge problem because American Airlines and British Airways awards are often cheaper than US Airways awards.
Refresher on Partners Sharing Space

To Suzanne Rubin, head of American Airlines AAdvantage,

In April 2014, American Airlines eliminated the possibility of stopovers on award tickets with no notice.

Previously, one stopover was allowed on one way awards--two on roundtrip awards--at the North American International Gateway City.

That rule gave folks who lived where there were no international flights on American Airlines partners the chance to enjoy their awards more with stopovers in major international cities like New York, Los Angeles, and Honolulu.

Finnair is offering excellent Business Class award space in a state-of-the-art bed next year from New York and Miami to Helsinki and beyond in Europe.

Since Finnair is a member of the oneworld alliance, you can book the business class award space for 50,000 American Airlines miles each way or 100,000 US Airways miles each way.

Finnair space is searchable on aa.com.

What is the Finnair Business class product?
What is the award space picture for Spring and Summer 2015?
How can you book awards with Finnair flights

Let me clear up one of the most common types of questions I get from beginners.

There is no transitive property of miles.

Just because Airline A partners with Airline B and Airline B partners with Airline C does NOT mean Airlines A and C are partners.

For instance, in yesterday's post Fully Flat Business Class to Europe for 25,000 Miles, I wrote:
I searched award space on Aer Lingus' routes from Chicago, Boston, and New York to Dublin for one passenger next April through July.

I searched on united.com.

This is the thirteenth post in a monthlong series that started here. Each post will take about two minutes to read and may include an action item that takes the reader another two minutes to complete. I am writing this for an audience of people who know nothing about frequent flyer miles, and my goal is that by the end, you know enough to fly for free anywhere you want to go.

I've covered how to earn miles and the redemption options for miles.

There is excellent award space in Japan Airlines First Class between San Francisco and Tokyo for most of the next 11 months.

Update 7/15/15: The best current offer is 75k miles:

For a limited time, the Citi® / AAdvantage® Executive World Elite™ MasterCard® offers 75,000 bonus American Airlines after spending $7,500 in the first three months.

American Airlines miles are the best for super-cheap economy redemptions and ultra-luxury redemptions. The Citi® / AAdvantage® Executive World Elite™ MasterCard® also offers Admirals Club lounge membership, meaning you can access over 90 American Airlines Clubsin airports around the world whenever you’re flying–even if you’re not flying on American.

American Airlines releases a ton of award space on its routes to Hawaii at the last minute.

On almost all of American Airlines' routes from Los Angeles to the four major Hawaiian islands and Dallas/Fort Worth to Oahu and Maui, there is award space for 4+ people in the next few weeks.

If you live in Southern California or North Texas, this is a great chance to use as few as 12,500 Avios per person per direction to get to Hawaii during high season when the weather is a perfect 85 degrees and sunny.

If you live somewhere else

American Airlines and US Airways are currently offering huge bonuses on transfers from SPG Starpoints.

British Airways has a unique, distance-based award chart that can provide fantastic value for short-haul flights.

Both Chase Ultimate Rewards and American Express Membership Rewards transfer 1:1 to British Airways Avios.

British Airways has access to all American Airlines "MileSAAver" award space. Furthermore, on some routes British Airways actually charges fewer miles for the same flight than American Airlines.

Unfortunately, using ba.com is not as straightforward as using aa.com.