This buoyancy is fairly weak on Earth, so it takes a large object to lift a small amount of weight. On Mars, there is so little buoyancy that it is very difficult to even make a balloon lift its own weight , let alone a payload of scientific equipment. Moving an aircraft through the atmosphere generates dynamic pressure which can be used to generate lift from the fluid motion around the vehicle. Wings are specially shaped to generate a large amount of lift while still keeping smooth, attached flow around them, thus keeping drag low. There is always resistance or drag on an aircraft as it moves through the atmosphere, whether it is lifting or not.
Additional drag is caused by the very wings that generate the lift.
Sometimes it is worth having an aircraft design that generates slightly greater drag if it satisfies another design aspect needed for the desired mission. Nevertheless, the drag forces must be overcome by propulsion systems that create thrust . Thrust is created by pushing some of the surrounding atmosphere back with greater velocity, or by adding extra material with high velocity to the atmosphere. For propulsion within the Earth's atmosphere, our systems rely on a greater amount of oxygen and a higher density of air molecules than are available within the atmosphere of Mars. These must be considered when designing a propulsion system for an aircraft to fly on Mars.