Does aa.com lock your rate while processing the booking?
 

Contrary to other airlines, AA.COM doesn't show a timer when you book. The timer is supposed to indicate that the rate has been locked and will expire in so many minutes in you don't complete the booking.

I'm curious if AA.COM has a similar timer, hidden in this case, or there is no protection of any kind at all until you end the booking process. I am guessing there is some protection lock, perhaps not from the very first step when you search for flights, but at least when you are more advanced in the booking process.

The moment you select your flight and proceed, AA creates a PNR in the background. If you open your "my trips" on a different tab, you'll likely see it.

It's valid for a period of time.

I've seen situations where, at checkout, you're told the fare is no longer available. So I agree it creates a PNR, but it does not seem to properly lock the fare. Then again, this could be some other issue -- I've seen situations where you encounter the "fare not available" issue, then start a new search and see the same fare again, yet find that it is still not available.

Are you attempting to book a fare that starts out of Google Flights or some other platform?

I've had this happen several times. Quite frustrating especially when on complicated multi city trips.

I believe AA creates the PNR in between the pax info page and the seat selection page (special meal page for long haul). That locks your fare.

If the seat is unable to be confirmed (for example, when someone snagged the seat before you, or weird married segment logic), you get kicked out to the flight selection page with a 'chosen fare no longer available' banner.

After the PNR is created, you have at least 15 mins to make the payment, provided you move your mouse every now and then to stop the page from timing out. If the page times out, or if you click choose another flight, the PNR is canceled. Otherwise it could actually stay live for a while in the background

Correct — this happens when credit card info bounces back as well or when the “this page has taken flight” error pops up. As others have noted, there is a PNR created and the seat / fare is held for a short period of time to either book online or via an agent.

Nope, I always start at aa.com

I've also seen phantom SWU space where it is advertised as available but then actually isn't, even when you call a CK agent for help.

Unless something has changed recently, Sabre holds the inventory when an agent or overlay "sells" the inventory into a PNR, BUT a fare gets validated when it's stored in the record (and again when ticketed). So you can actually be holding the inventory you need for your transaction, but have the transaction fail on a later step on the web (or even an agent on an overlay or manually building a record at a help desk or agency) because the fare itself is no longer available when it tries to store the fare after selling the inventory. So basically there are two moving parts -- one the reservation system protects you for a while on, and another that is always subject to change even during your transaction.