Any fixed wing drones would need a flat airfield to take off / land
I think you’re still using Earth’s atmosphere (and gravity) for what you have in mind. For one, you only need and airfield to land if you ever intend to land. We already have fixed with aircraft that can fly continuously for 90 days at a time. Mars gravity is only about 1/3 of Earth’s which helps, but it also has a much lower density atmosphere which hurts. Second, you only need an airfield to take off, if you’re already on the ground.
Perhaps one far future approach is to build a fixed wing aircraft that would fly continuously, and could perhaps deploy its wings during descent into Martian atmosphere on arrival negating the need for it to ever touch the ground as part its mission.