A laptop bomb would presumably be fairly small in size and would probably have to be placed directly against some sensitive part of the plane in order to be effective. The cargo hold meanwhile is already reinforced and any bomb would most likely end up in a middle of a lot of baggage that would absorb most of the blast. It would probably force the plane to make an emergency landing but it's unlikely to be catastrophic.
The risk with laptops in the cargo hold isn't the blast force of explosions causing a hull breach, but fires. Now any terrorist who wants to bring down a plane simply needs to rig their laptop batteries to catch on fire, which is much, much easier to do than rigging it to explode.
Batteries contain their own oxidiser and fuel, so the only way of extinguishing a better fire is to remove the heat (fire triangle: fuel, oxidiser, heat).
The best lay-person's method for extinguishing battery fires is flooding with cold water, which will be hard on an airplane at the best of times.
Here's a video of a lithium battery fire in a cargo hold, as you can see it causes an explosion and swiftly a fire that burns the entire compartment. If you imagine every checked in bag containing a laptop, you'd get a similar effect if you rig one to catch fire.
Note that the video claims it's 5000 Li+ batteries. It's hard to tell from the video, but it looks like it was ~4 boxes filled with only the batteries. Even a large pile of laptops (no bags) would have a hard time making the explosion[1] in the video. If you separated each battery+laptop into separate bags, the density of Li is so low a single battery burning/exploding may not even reach the other batteries.
[1] obviously a fire is still possible, even with a single battery
Yes I guess it would only contain a few hundred laptops if they force all into the hold. I imagine a fire is quite possible though from a rigged laptop (or just an accident) and impossible to put out, unlike a fire in the cabin.
This was answered and discussed at length in the article
>The battery bombs would need to be manually triggered, a source explained, which is why the electronics ban is only for the aircraft cabin not checked luggage.
Obviously stuff in the cabin are much easier to access and manually manipulate than stuff in the cargo hold. Im also very disappointed at the slew of other answers and their up-voters who clearly did not read the article.
A bomb that size would be very unlikely to take down a plane (remember, blowing a hole in the fuselage doesn't cause people to fly out, despite what the movies show), so it seems the most likely use for it would be to try and blow open the door to the cockpit so they can take over the plane.
Regardless, though, it's incredibly stupid for the US to even consider this ban. The chances of success are extremely small compared to the headaches this will cause.
A bomb hidden in the cargo hold is effective if the intent is to simply blow up the plane by timer/remote/altitude. But if the goal is to hijack the plane, then a bomb in hand could be a more convincing negotiation tool.
