Yeah not trying to poo on them....everyone makes mistakes. That said, it's a pretty good idea to be generally familiar with what your aircraft can do and what it cant do, given a fuel load and the winds that are on the -1 (or whatever product they were using). JMPS and/or PFPS are great tools for doing quick flight planning, but you have to sanity check it....the whole garbage in/garbage out deal. I'm not a P-3 guy, so I can't QB their thought process, but in my aircraft, I know generally without crunching numbers how far I can get with calm winds, with a strong headwind, or with a lot of draggy stuff hanging off the wings. These aren't estimates that I would bet my wings on for flight planning purposes, but they are estimates that can tell me if the fuel plan I generate is absolute garbage or if it seems reasonable. That all said, it sounds like the over-estimate was not nearly as bad as it appeared from the OP, so maybe not something that they would have been able to notice until they had been airborne for a while. Either way, they made a good decision, saved the airplane, saved their wings/etc, and lived to fly another day so that sounds all good to me.