For high altitude platform (HAP) communication systems, this paper analyzes the wireless transmission performance under an integrated scheme of space division multiple access (SDMA) and non-orthogonal multiple access (NOMA) based on stochastic network calculus (SNC) theory. First, under the condition that only user location information is available, a user clustering algorithm based on the K-means clustering algorithm is proposed. Then, in scenarios where the HAP is equipped with a uniform linear array, a hybrid multiple access transmission scheme is proposed in which inter-cluster users employ SDMA, while intra-cluster users adopt power-domain NOMA. Furthermore, considering that the HAP-to-user link follows a Nakagami-m distribution, closed-form expressions for the upper bound of the system delay violation probability and effective capacity are derived based on SNC theory for both successive interference cancellation (SIC) and joint decoding (JD) schemes. Finally, computer simulations verify the correctness of the theoretical analysis and reveal that the JD decoding scheme is superior to SIC in reducing system delay and enhancing effective capacity.