Overall, that’s not too little; however, it must be understood that it detonates not when it sticks into an airplane, but when it is still at a certain, and fairly significant distance. Moreover, the main strike factor is not the blast wave, but far more significantly – the stream of fragments. These fragments are previously prepared rods (and in the earlier versions – little cubes, if I recall correctly). And yes, for a jet fighter, that, in itself, is more than sufficient.
However, here we are dealing with a huge airliner. Yes, one rocket will rip the casing, cause depressurization, and will kill a lot of passengers. But it will not break up the airliner into pieces. Given certain conditions, the pilots may even be able to land it. And, in fact, there have been precedents (to be provided in future posts). For example – the very same An-28, which is alleged to have been the first victim of a BUK system; even though it was done for, but the crew was able to successfully catapult out. Which, in some way, symbolizes. An An-28, by the way, is far smaller than a Boeing.