The few pilots I've known (small aircraft) have generally agreed that the most common reason for engine failure is water in the fuel. Since water is heavier than the fuel, it sinks to the bottom of the tank. Most pilots will drain a cup or so of fuel out of the tank prior to every flight. Some pilots forget, are drunk, are thinking about other things, or don't think it's necessary.

Some pilots fly too low over ridges and get caught in downdrafts. Some don't pay enough attention to their altimeters, or didn't adjust it for the barometric pressure, or don't really know what the elevation is of the terrain they're flying over.

Always ask the pilot if he/she has filed a flight plan. Or be with him when he does it. If you're too embarrassed to ask, you're too dumb to fly. If he/she says something like, "What's wrong, don't you trust me?", say "Not with my life, no."

A little Cessna 150 can go over 300 miles on one tank (depending on the plane, the load and how much throttle the pilot uses). That distance would provide a search area of over 70,000 square miles, about the size of Missouri. With two skinny people on board, no cargo, a tuned engine and a decent tailwind, maybe about 500 miles, so you can kick the search area up to almost 200,000 square miles (three-quarters of Texas).

Good advice seen here before: "Dress for egress" and "Dress to survive, not to arrive".

Sue