This paper considers a dual-system model consisting of an unmanned aerial vehicle base station (UAV BS) enabled communication system for suburban service and a reconfigurable intelligent surface installed UAV (RIS-UAV) relay assisted communication system for urban service. The dual-system rate is maximized by jointly optimizing user scheduling, phase shifts of RIS, power allocations of UAV BS and ground BS, and dual-UAV trajectories. The original non-convex optimization problem is decomposed into four sub-optimization problems, including user scheduling optimization, phase shift optimization, power allocation optimization and trajectory optimization. Then, we propose a four-layer alternating iterative optimization algorithm to achieve the suboptimal solutions of the original problem. Simulation results show that compared with other benchmarks, the proposed optimization algorithm can significantly improve the average dual-system rate.