In flight, yeah totally impractical and not worth even trying.

Theoretically, if I were to attempt it, I’d get my liquids through the checkpoint, mix them together and then wait the few hours for the precipitate to fall out. Then go to the bathroom pour that through a handful of paper towels, or even some coffee filters I brought in my carry on. Then, put that into some type of confinement like a metal water bottle. Lined with paper towels to pull the last bit of moisture out of the crystals. A couple more hours later and there’s a pretty sensitive device that could be set off dropping, throwing, hitting, or whatever.

That’s a way. There’s many, many ways that someone could go about it. Also agree with the sentiment that the TSA is complete theater and doesn’t actually do much to keep anyone safe. But they’re working government jobs, getting paid ok-not great, with decent benefits and can get a retirement out of it.

The shoe bomber had what was probably good quality stuff, but he was missed his flight due to looking suspicious and being pulled for questioning, he stayed the night at the airport all the while walking around with these shoes that were hollowed out on the bottom. Probably nervous as hell and sweating all this time, plus walking through puddles and such. He managed to dampen the crystals so the next day when he got on his flight they were too desensitized to detonate.