No smoking in airplane bathrooms

[snopes]

Comment: I heard from someone (I
can't remember who ... a flight attendant maybe?) that tamping with the
smoke detectors in the bathrooms of airplanes became illegal when the
crack epidemic hit. The idea was that people couldn't go without their
fix for an entire flight and went to the bathroom to smoke rock. I
queried a group of friends last night and someone told me that the rule
was instituted after a Swissair crash in the 1980s.

[Mateus]

The wiki page for Swissair accidents doesn't list a crash in the 1980s (one from 1979 due to overshooting the runway; the next came in 1998 from an air conditioning malfunction).

[Lainie]

ISTR a problem with a fire in an airplane, not a crash but a forced landing, after which smoking was banned.