Assuming you want to cancel frequencies up to 1kHz, you're going to need mics every 30cm at least for a useful sound field. For a 787 fuselage, that's about 60 around by 190, let's round that down to 10000 microphones. But of course, then you need electronics for them, and a way to carry the signals back to somewhere for processing. That's about 10 Gbps of data, fine, doable, but then you need to process it. Since you need to cancel separately per passenger, that's 2.4 million filters (10k mics * 242 passengers) to process. Nevermind that since this is a plane, there is a huge amount of overhead due to safety requirements.

This is all assuming this whole idea works, which it probably won't, because it's not just about the microphones on the fuselage but also how sound is transmitted inside the plane and other noise sources.