Clare, the current aircraft I own, the guages are 47 years old, they've been calibrated as required. When I was 47 years old, I was calibrated yearly, but I still couldn't run the 100m at my 18 year old time (i was pretty quick). If my fuel tanks sprung a leak I reckon I'd pick it up before I got airborne. If I could I'd post a video of a leak I did find, I would, it wasn't the tank, it was the line that came down through the centre pedestal in the Cessna. I digress.
If a tank sprung a leak in this incident, it obviously wasn't picked up by the guages, as the aircraft ended up in the drink. Kinda proves my point right?
And I also didn't say that you couldn't use them to confirm, I said I don't trust them and won't ever. The only fuel guages that I found reliable were in the turboprops I've flown.
I'm hoping that someone can find the cause of this, it will help all of us.