They've added a new test, for explosives residues, to the check-in security procedures. State of the art being what it is, what the sniffer machines are actually looking for is nitrate residues (and maybe other things as well, but never mind that). Explosives tend to leave nitrate residues. So do agricultural fertilizers. We'd just spent 3 weeks riding and (occasionally) camping in America's agricultural heartland. Everything we had tested positive to their sniffer, which meant an almost complete unpack and visual check.

It's comforting, sort of, to know that these things really work. On the other hand, as a practical matter, if you'll be flying out of a tour where you've been riding in large-agribusiness areas, you might want to arrange a rest day or two in your exit-airport city before you leave; a laundromat, wash-everything day or two. And/or, allow yourself yet more extra time at the check-in.

Also (side effect of the same thing) at the moment 2 hours really isn't enough time for a comfortable connection if you're coming off an international flight in the US, and transferring to an internal flight. Since you pick up your baggage to go through customs (even if it's been notionally 'checked through'), and so could have moved forbidden things from checked to cabin or vice versa, they recheck everything during the transfer. The new test really slows that down. (We came within minutes of missing our connecting flight.)

The new test is intrinsically unwieldy, and to make things worse it's not yet really integrated in with the older security measures which slows it down even more. So, I'd expect improvements in the future. For the time being, though, keep in mind that you may need more time in the airport than used to be the case.

-- http://www.cse.bris.ac.uk/~ccpes --- http://www.bigduck.u-net.com/