Lufthansa from Boston to Frankfurt in the mid 90s. I was happy to get on standby. Settled in my seat. A guy in orange mechanic uniform strode down the aisle. Announcement informed us that the toilets weren't flushing. The mechanic left and announcements told us that the mechanics couldn't fix it and they were going to attempt to reboot the plane in case it was an electronics thing and we all had to deplane. First class pax were shunted into the last flights out to Europe. The rest if us got off , hung out and watched the plane being rebooted. Of Course it didn't work and the flight was cancelled. The pilot flew it to Frankfurt anyway, sans passengers.