They now say 7-8 hours of flying after Malaysia, which could even take the plane to Yemen (or maybe not, if it has to fly below radar. I find it inconceivable that it could have flown over India without being tracked.
7 to 8 hours after it departed Malaysia, or after it disappeared leaving the Malaysian coast? All reports I heard said 5 or 6 hours of fuel from the time it disappeared. Which is reasonable. The heavier you are, the more gas you need, which means taking extra gas is a waste of money. In the case of a 777 on a 6 hour flight, having 2 hours of reserve (which would be 8 hours from take-off) is even a little much (about an hour at cruising speed is a good rule of thumb, though the actual rule is quite specific and varies from region to region), but it's not unreasonable. That's only thousands of wasted dollars, one hour would be more realistic. If you mean 7 to 8 after it disappeared, that's a ridiculous amount of gas. The cost in hauling that extra fuel would eliminate virtually any profit from the flight and chew it into a losing proposition. Which is why when the Captain (or First Officer) would've asked for that load, Malaysian Airlines would've questioned it. And they would have known. The flight calculations are done by the pilots, true, but they are also done by the flight computers, by flight management systems and by the airline's dispatch department, who would've received data from the airplane detailing its own calculations. It would not have gone unnoticed that the airplane was carrying enough fuel to chew threw 10's of thousands of dollars of lost revenue.
And if it's flying under radar, cut its range in half or more. A jet engine is extremely fuel-efficient at high altitude and high speed. It's extremely fuel-inefficient down low in the grass. Also, being down below radar coverage over land means staying REALLY low. Low enough that people in India would've been calling in reports of a plane crashing non-stop. Toronto gets lots of "A plane is crashing!" reports from planes over the GTA enroute to YTZ, YKZ and YYZ, imagine how many reports would come in of a huge airliner screaming past overhead a mere few thousand feet above the ground over areas not close to airports used to traffic, like over Barrie or Grand Bend for example.
The other factor is that, despite what "experts" say on CNN, it's not easy to disable communications. And for good reason. A hijacker charges into the cockpit and, knowing the basics of aviation, advises the pilot he knows about emergency squawk codes and code words, and advises you to disable the transponder and turn the radio off. It's a very possible situation. So one of the built-in redundancies is to remove some communications from the pilot's control. Things like ACARS are automatic redundant systems. To turn off ALL communications, you'd need to get out a big honking manual, isolate where the circuits are tied in, and start pulling circuit breakers. Which, to do safely, would involve following multiple long, complex checklists to make sure you aren't turning off something important. We don't remove ALL communication from the pilots control because very few people understand what ACARS is, let alone how it works. A terrorist who goes off and gets a pilot's license will know about emergency squawk codes and the like, but probably won't realize there's a magical stream of information flowing from various systems to the airline and the aircraft manufacturer, so he'll feel confident after he's had the radio and transponder turned off. And making them comfortable is good. It keeps them from hurting people or panicking.
I heard one "expert" say that all systems need to have the ability to be disabled for safety, such as to prevent the spread of fire. But that shows a lack of understanding on how these systems work. In fact, if you look at the QRH (Quick Reference Handbook) for basically ANY Boeing airliner (which is what I fly), you can see the "smoke, fire and fumes" procedure is very short. If you're a private pilot, you likely remember that step one in a cabin fire is the electronics master. It's simple because the aircraft is designed for stick-and-rudder flight. Aside from fancy equipment like a GPS and a radio, which aren't really necessary to avoid plummeting, electronics have no effect on your aircraft. In an airliner, step one is to put on your oxygen mask and smoke goggles, step 2 involves venting to clear the smoke, and step 3 is to start the diversion process if the smoke doesn't start going away. There is nothing in the emergency checklist that says start turning off electronics because it's a bad idea to do so blindly. You won't find those details in the QRH. The most the QRH will say is if you can easily determine the cause and locate the circuit breaker, trip the circuit to disable the equipment and continue or divert at the crew's discretion. Turning off ALL electronics just isn't done in an airliner. So having multiple connection points to multiple buses for critical components, which include the majority of things like black boxes and ACARS since they can help locate or isolate the cause in the case of a crash, is just common sense. If a component being off means the plane can't fly or disables critical safety systems, there's no reason to give a pilot easy access to disable them.
The idea that a pilot can make a plane stop transmitting everything is pretty out there. It's not impossible, but it would take a lot more knowledge than even your most experienced pilots. We're talking months and months and months of premeditation. It's not impossible, but it's EXTREMELY unlikely. And it certainly could NOT have flown across a populated country. It would've been caught on radar or visually reported at some point if it had tried to do that. What remains the best explanation is an electrical fault that caused a catastrophic failure of the electrical systems. A fire can spread quickly, so quickly that all communications and electronics could've been disabled, or a failure of some critical part of the electronics system that caused all electronics to stop transmitting. While the question remains "Where is the evidence of a crashed airline then?" you have to bear in mind that none of the other proposed scenarios (except maybe "aliens beamed it away") explains why there's no evidence of wreckage or diversion either. But at the end of the day, the most likely reason for an airplane to completely disappear from every single communications system is a catastrophic failure of all electronics. I'm not saying all other ideas are impossible, but they are less likely by a mile based simply on how these aircraft are designed.