[Aussie Ann]

I'd rely on Imodium. I've got a 24 hour flight ahead of me in a month's time, and I'm not going to take any chances. I'm going to increase my daily dose of Imodium from about 24 hours before the flight (ie, before the diarrhoea gets going), and then keep taking it during the flight, right up to the maximum daily dose if necessary. I don't see the harm in doing this on occasion as you say, purely for peace of mind.