US Airways has been the leader in monetizing their frequent flyer program, offering more and bigger promotions than pretty much anyone else including to straight up buy miles. They offered something along the lines of a 100% bonus on purchased miles for nearly 10 months in a 12 month period beginning November, 2009.

And then they went silent. After a monster holiday shopping promotion at the end of 2009, the 2010 version was a thud. And they haven’t had buy miles promos for the past couple of months.

While US Airways had developed a reputation as the ‘consolidator for Star Alliance premium cabin seats’ (they were selling miles cheap, those miles then would be used for premium cabin awards on their partners, effectively selling excess inventory — those seats released as awards — for a deep discount, since you can hold an award without the miles in the account, it was a sure thing, reserve the seats and then buy the miles).

But more recently it’s become increasingly difficult to redeem with US Airways. Their systems were ‘unable’ to see Lufthansa first class award space between the US and Europe, and much speculation ensued that they were ‘blocking’ that space so that members couldn’t redeem for it, much like United has done at times when Mileage Plus didn’t want to pay their partners for the award seats that were being offered.

That became more or less a non-issue, as at least on Lufthansa’s 747s they’ve stopped offering award seats in first class most days into the future, as they reconfigure their first class product on the aircraft with new seats but only 8 rather than 16 seats. Of course, inventory on the Airbus routes remained. And there have still been occasional odd dates with first class award space even on 747s.

And then there were reports that US Airways was having problems booking available award seats on other partners as well, prompting much consternation and speculation.

The worry of a full Starnet Blocking system as has existed with United, coupled with a lack of promotions like the 100% bonus on purchased miles coming back, has generated some speculation that US Airways finally decided that while they generated some cash, in the long run it was too costly to do so in the way they had been going about it.

Except now they’re back but only for some members. I just received an email as follows:

Get 40% off your purchase of Dividend Miles

Thank you for buying, sharing or gifting Dividend Miles in 2010!

We’d like to help you earn more miles this year. Enjoy 40% savings
when you buy Dividend Miles before January 31, 2011.

This exclusive offer is just for you* and you can only get it here:
Buy up to 50,000 Dividend Miles and Save 40%

P.S. Your discount will appear on Step 2 once we have validated your account.

The 40% discount doesn’t show up on US Airways.com. Apparently it’s only available to email recipients, and only by using the email link. The offer lasts through January 31 and applies only to the first 50,000 miles purchased. Instead of a bonus of additional miles, it’s a discount on the purchase of 50,000 — encouraging you to purchase 50,000 miles, rather than encouraging you to acquire 100,000.

Put another way, they’re angling to get you to buy miles to save towards future awards, not to buy and cash in in the same transaction for premium cabin international seats on their partners. (You can of course top off an account to do so, but they’re not giving you a bonus that lets you do it solely on the back of the offer itself.)

So perhaps they really are tightening, even as they continue to push their bonuses and monetize the program. Not surprising at all, the gravy train couldn’t last forever.