That's an interesting point of controversy. Supposedly (and I only know this from some of the reading I've done recently), that footage was never supposed to represent a bombing attack. The explosions shown are actually footage of the demolition of the sets- the Philippine government required all sets to be blown up, and Coppola decided to film it. This was then included at the end as a way to show the credits, but it was never supposed to represent the bombing of Kurtz's base. FFC changed this for the redux b/c people were misinterpreting the footage, and now shows the credits differently.