Matt Simmons, who writes the Standalone Sysadmin blog, has been wondering why there are ashtrays in airplane toilets, even though you aren't allowed to smoke anywhere on or near an airplane, and you haven't been allowed to do so for quite some time. It turns out that airplane toilet ashtrays are mandatory: "Regardless of whether smoking is allowed in any other part of the airplane, lavatories must have self-contained, removable ashtrays located conspicuously on or near the entry side of each lavatory door, except that one ashtray may serve more than one lavatory door if the ashtray can be seen readily from the cabin side of each lavatory served." (Code of Federal Regulations for airworthiness). Simmons explains why:
The plane can not leave the terminal if the bathrooms don't have ashtrays. They're non-optional.
That's an awfully strange stance to take for a vehicle with such a stringent "no smoking" policy, but it really does make a lot of sense. Back in 1973, a flight crashed and killed 123 people, and the reason for the crash was attributed to a cigarette that was improperly disposed of.
The FAA has decided that some people (despite the policies against smoking, the warning placards, the smoke detector, and the flight attendants) will smoke anyway, and when they do, there had better be a good place to put that cigarette butt.