A use for low occupied planes on 9/11

So, a lot of people mention a lack of full planes on 9/11. Claim it's suspicious, means they could all be put on one plane etc. What if they needed to be?
Would it be a possibility for whoever did it, to put some sort of explosive in the planes? If there were some in the fuselage, like an armour piercing weapon, or lots of smaller ones, like a cluster bomb, could that not account for some of the reports of explosions? If they were also set up to detonate at a certain time, to take out the core as well to finish the job, is it impossible?

This way you don't need to make sure the planes hit the building in the right place for your explosives, since the plane carries them in, doing that bit of the job for you. Of course, you'd need to fireproof them a bit, but we're all agreed there was almost no fire anyway, right?

Hence, the planes had small occupancy, to allow a large enough payload within the MTOW.

I'm not saying thats whats happened, just exploring an idea based on the low occupancy.