Naps tried that in WWII. Firebomb balloons. Did not end well for them.
Drop a container full of bats that are released before it lands. The bats had a small incendiary device on a timer. The idea was the bat would get up under an eave or into a Japanese building. Most were wood or straw and very flammable.
We ended up not using them as they were not deemed viable.
However, during testing, we did end up burning down some of our own buildings by accident!!
When I read that I thought “It obviously works! Why not viable???”