US airlines generally allow you to book miles at a ‘saver’ or ‘low’ award level, and at a more expensive price point that offers greater availability.

The old standard used to be that spending ‘double miles’ would get you any seat, any flights. That’s how it worked at American for the most part until April 8.

• Alaska, Amterican, and Delta now offer multiple tiers of prices.
  
• United doesn’t offer ‘last seat availability’ to general members who are not co-brand credit card holders. Last seat availability is offered only to folks with the United Explorer and Club cards and to elites.

The idea of spending extra miles to get the seat you want isn’t universal, you can’t do it with British Airways or Virgin Atlantic miles for instance. Most European and Asian carriers don’t offer this, actually, although some do — for instance Singapore Airlines has 3 award levels.

A frequent flyer program can generally only access these more expensive award levels on their own airline and not on partners. There have historically been some exceptions, but that’s been rare. You can’t spend extra United miles to redeem for any Lufthansa seat, for instance, even though the two airlines are ostensibly ‘revenue-neutral’ joint venture partners across the Atlantic.

Since American and US Airways merged they have been run in some ways jointly (the same people increasingly running the same functions at both airlines in many cases) but in other ways separately. You couldn’t spend American miles for extra award inventory on US Airways, and you couldn’t spend extra US Airways miles for extra award inventory on American.

I didn’t expect that to change until the frequent flyer programs actually combined in the next few months. But the functionality has been added to both the US Airways and American websites (and to their call centers).

Here’s an AA.com award calendar screen shot showing only extra award availability for non-stop flights, Washington National – Phoenix, a route served by US Airways.

Before you would see only grey — nothing available — because there was no higher-priced extra award inventory using American miles for US Airways flights. Now every date is green (available).

The prices vary by calendar date. The price of a ‘saver’ award is 12,500 miles (not displayed via this search) while extra availability one-way domestically may cost 20,000, 30,000 or 50,000 miles.

You’ll see that Friday, July 3 brings up non-stop flight options for 20,000 miles. It’s definitely ‘off-season’ for spending the weekend in Arizona (hint: hotels are cheap and deserted, I find it a rather nice time to go!).

The US Airways website now works in much the same way. I searched non-stop flights Austin – New York JFK (which are operated by American). Here’s the availability calendar.

Prices above the saver level are color-coded as follows:

You can now book a ‘medium’ (or higher) American flight using US Airways miles:

Update 8:43pm Eastern: There’s some glitchiness on the US Airways side booking American AAnytime awards. They’ve suspending the ability to use US Airways miles to book last seat availability on American until they fix the issue. You can still use American miles to book last seat availability on US Airways.

Update February 10: Availability to use US Airways miles for American AAnytime awards is back — but you have to call US Airways reservations to book.

---

You can join the 50,000+ people who see these deals and analysis every day — sign up to receive posts by email (just one e-mail per day) or subscribe to the RSS feed. It’s free. You can also follow me on Twitter for the latest deals. Don’t miss out!