I don't disagree with that except modern fly by wire systems involve redundant cabling so it's much harder to cut them all. But, yes if you know the weak points and have unrestricted access a few pounds of High explosive is enough.

The point is without that knowledge and access by the time you have enough HE to take down a modern jumbo jet you can also use it to kill a very large number of people in other ways.

Remember, most bombings are really poorly executed at a technical level. Army's use grenades because they work. If you want to do as much damage to a crowd as possible your better off with a large number of fragmentation grenades than a suicide vest. Create a choke point, detonate something to create a crush, blow up the densely packed crowd.

PS: Mortars are frightfully effective yet tiny.