1. They didn't run out of fuel
2. They knew exactly how much fuel they had
3. when mum passed her position (Via a Bag) the ship was not where they it was supposed to be
4. The crew then decided that they couldnt make it and so in order to save 3 lives the AC decided to put the aircraft in the water and get out.
"Lets face it, most Pussers grey funnel line steamers are not exactly 100% reliable when it comes to land on position"
- actually the T22 and T23 are pretty good. But the T42 has a nav system which Vasgo de Gamma invented and then ditched because it was obsolete. The T42 is renowned for nav slippage, so much so that the last time I operated on a T42 (after a similar incident) I refused to go outside of 50 miles from the ship.