Assuming the pilot doesn’t push the stick “over” it will glide for miles, depending on your starting altitude and sink rate. The crew of a Canadian 767 had to dead-stick their jet into an abandoned CFAB base back in 1983, due to a malfunctioning fuel management system and poor “by hand” calculations. As a result, they took off with barely half the fuel needed for a flight from Ottawa to Edmonton.
The incident has become known as the Gimli glider, after the former Canadian AFB facility where they landed. It was also made into a fairly entertaining TV movie starring William Devane.
http://hawaii.hawaii.edu/math/Courses/Math100/Chapter1/Extra/CanFlt143.htm
Of course, the pilots of the Canadian 767 were trying to get their aircraft—and its passengers—on the ground in one piece, unlike the Malaysian pilot who flew that 777 into the Indian Ocean.
Do you happen to know if the Auto pilot would automatically assume a glide path if the crew were comatose/dead and not in control of the aircraft. ?
There’s an additional proviso here too: They had help from the ground.
One thing that really needs to be answered is “was there an on-board fire in the cargo hold?”
That could explain quite a few things we’re seeing here.
Referring to the 777, assuming it's on autopilot and no pilot input, when fuel runs out and it starts to descend, the AP will disengage, and the aircraft will continue to glide in the trim attitude the AP had used. The normal glide ratio of a large swept wing transport is in the 20 to 1 range. So, if it was at 35,000 (about 7 miles up) it would glide 140 miles at most.