I've written before about the lie of "no-blackout-date" policies at major hotel chains. By guaranteeing access to any standard room at a fixed redemption rate, hotel loyalty programs stave off open revolt from their most desirable properties by refusing to enforce those guarantees.
The US domestic air carriers avoid a similar problem by employing various forms of variable award pricing on flights operated by their own aircraft (partner awards are typically only available at the lowest level). With United Mileage Plus, American AAdvantage, and Alaska Mileage Plan that takes the form of a award chart with one price for a limited number of seats released, and then the ability to purchase all or some of the remaining seats at a higher rate.
Delta SkyMiles chooses not to publish an award chart, so award redemptions on Delta-operated flights cost whatever their website or phone agents say they cost.
Why I love last-seat availability
Many travel hackers seem to make it a point of pride that they will only book award tickets at the lowest award levels. I do not.
I travel hack for two reasons: I love to travel, and I cannot afford to travel as much as I would like to (thanks to all my monthly subscribers — you're doing your part to help!). I square that circle with travel hacking: if I can earn points cheaply enough, then I can redeem them for flights I want to take without paying anything close to the retail price of those flights.
The phrase here is "flights I want to take." If I'm traveling to the Western Montana Fair to catch the rodeo, then I sure as hell better get there in time to see those cowboys. If I want to attend a brother's graduation, I need to get there before he walks, whatever award availability happens to be (usually not great around cap-and-gown season).
Last seat availability on the domestic carriers allows me to take the flights I want to take to get where I want to go, when I want to go there.
I traveled before I travel hacked
What informs my attitude is that I traveled almost as much before I started travel hacking as I do now that I write a slightly popular travel hacking blog.
And it was horrible!
I once flew on Spirit Airlines between Los Angeles and Chicago because that was the cheapest flight when I hit "sort by price" on Kayak. No Big Front Seat, no assigned seating at all, in fact, and my knees drawn up so close to my chest for the 3-odd hours I'm still slightly surprised I survived.
Now I can pick the flights I want, and either pay for revenue tickets at a steep discount thanks to the miracle of price compression, or book award tickets, whether it's at the lowest award pricing level or not.
Know your trade-offs
Now, many readers no doubt object that booking at anything but the lowest award level is a "waste" of miles. After all, booking a 30,000 AAnytime one-way award ticket instead of a 12,500 SAAver award ticket costs an extra 17,500 AAdvantage miles — almost enough for a one-way award ticket to Europe during low season. If you don't have enough miles to pay for your award trip to Europe, you'll have to (insert gasp) pay with cash!
Those might be your trade-offs, but they aren't my trade-offs. When I run out of miles (God forbid, but let's entertain the possibility) and money, then I'll stop traveling until I have more. I have to prioritize the trips I really want to take, then use my leftover miles to jaunt around the world. Fortunately, I have a lot of leftover miles. But when I run out, I won't regret the fact that I took the flights I wanted to take, at a fraction of the price I would have had to pay in cash.
Ultimately this comes down to earning your miles and points as cheaply as possible. If you're earning 1 SkyMile per dollar spent with a Suntrust debit card, or 1 AAdvantage mile per two dollars spent with a UFB debit card, every flight operated by Delta or American will always be cheaper with miles than with cash.
By all means, book the cheapest flights that work for you! But what travel hacking has made possible for me is to have a slightly more expansive definition of what "works" for me (that was my last Spirit Airlines flight — and good riddance).
Bonus last-seat availability: I love Amtrak Guest Rewards
No discussion of last-seat availability would be complete without mentioning the wonderful Amtrak Guest Rewards program, which (besides some rather inconvenient blackout dates seeming mostly to do with the school year and national holidays) allows points to be redeemed for every single seat, every single roomette, every bedroom, and every family bedroom on every single train (and connecting Thruway Motorcoach) offered by Amtrak. There is no such thing as "award" availability; if you can buy it with cash, you can buy it with points.