You can probably get through with a 6-8" piece of threaded pipe, some ends, a box of matches and a cotton fuse.
An 8" pipe bomb would seriously create a potential crash and large loss of life.
The thing is as the site says, most of the 'terrorists' out there already know this shit.
A 2L soda bottle, some aluminum foil and a little pool acid is a decent bomb too.
Yeah I'm not saying they can't still find a way to destroy a plane if they try hard enough. I'm saying generally that they won't get control of one again, at least not the way they did last time. Even more generally, I'm saying that the content of the posted site is fear-mongering bullshit.