It's not just AMC, it's Cinemark too.
At 11 a.m. CT, I logged on and just sat there, dumbfounded as NONE of the North Texas IMAX theaters had NO IMAX midnight showings available. In fact, you couldn't even buy a regular ticket until about noon, 1 p.m. CT for AMC.
Then around 2 p.m. CT, the Cinemark tickets went on sale, but only regular no IMAX. It was excruciating. That's when I hopped on the Fort Worth Museum of Science and History (which has an Omni IMAX -- true 70 mm) on a complete hunch...they hadn't advertised they would be doing any TDKR showings AT ALL. And of course, they had tickets up for sale, since 11 a.m.
I swooped up as many as I needed for my friends and now I'm all set while the four to five other IMAXs in DFW STILL haven't released midnight showing tickets yet. It's a shame.