Airfoil

Airfoils (Element) provide atmospheric lift to construct in proportion with its velocity. They do not consume fuel but demand proper placement for optimal usage. There are 3 types of airfoils, each providing a difference between how much drag they cause or how easily they stall.

Drag
Drag is a force generated by a solid object that moves through a fluid (the air for example). For drag to be generated, the solid body must be in contact with the fluid. If there is no fluid, there is no drag. Drag is generated by the difference in velocity between the solid object and the fluid. There must be motion between the object and the fluid. If there is no motion, there is no drag. This is important to know because airfoils do not work in space. In short: If your ship has a lot of drag, it will be hard to move it forward or get it into the air.

Stall
Stall is defined as a sudden reduction in the lift generated by an airfoil when the critical angle of attack is reached or exceeded. Or: a stall is a reduction in the lift generated by a foil as angle of attack increases. In short: if you try and lift your aircraft too fast with small airfoils, they will stop creating lift.

Lift
So obviously you want a lot of lift on your ship and you want to maintain it at all times during your take-off. A big airfoil will catch a lot of air but it puts an immense force on your machine at the same time. Finding a balance between how fast you can move forward versus how fast you can leave the ground is a balancing act. Different airfoils exist for different reasons, for example: you want a light fighter to be able to move forward really fast, generate a lot of lift that way and take off quickly. A big freighter will move slow by nature and already create a lot of drag on its own, so just making sure it can take off at all is a priority.

Aileron
An Aileron comes in a regular and compact version, both ranging from XS to M. These airfoils create the least amount of drag, but they stall very easily.

Stabilizer
A Stabilizer is the exact opposite. They cause a lot of drag, but have a very high stall angle. They range in sizes XS to L

Wing
A Wing offers a good trade-off between drag and stall angle. They range in size from XS to M with a variant on the M sized as well. It might seem obvious, but It is the reason why nearly every ship has at least 2 wings, if the size of your machine allows for it, you can go up to 4 or 6 wings but maybe other components might do the trick just fine of getting you airborne while minimizing drag. Or if you really can't get your ship up fast enough you might need fewer wings and more stabilizers.

Sizing
The different sizes increase their stats. An XS Wing will provide a maximum lift of 62500 N and the M Wing will provide a maximum lift of 1000000 N. You might be included to equip your craft with the biggest wings and be done with it, but if they create too much drag for your engines to overcome, it will go nowhere.

Element Stats
By opening the marketplace in-game (J) and navigating to the desired airfoil. You will have the ability to open a details panel by clicking the arrow next to the parts name in the top-right of your marketplace interface. Here you can find everything you might want to know about your new airfoil.