Most image encryption techniques are proposed to be applied to the whole image, which lacks the focus of information value. In this paper, we propose a target-based image encryption scheme. For remotely sensed airport images, we first take the aircraft considered to be sensitive information as the target and detect its positions. And then perform the proposed three-dimensional bit disorder method (3DBDM) and the arbitrary point dynamic diffusion on these regions. Finally, encrypt the entire image through high-speed index-dynamic diffusion to improve efficiency. To obtain a more stable key stream, a new ill-conditioned parameter infinite-interval chaotic system (IPIS) is introduced. The evaluation of IPIS shows that the introduction of ill-conditioned matrix brings higher sensitivity, randomness, and wider chaotic interval, which potentially improves the security of chaotic image encryption. In particular, the encryption method for aircraft regions can be generalized to ordinary images. Various encryption effect tests verify the security and practicability of the proposed algorithm and target-based encryption scheme.