1. Picture: Design of a Flying Machine (Public Domain)https://commons.wikimedia.org/wiki/File:Leonardo_Design_for_a_Flying_Machine,_c._1488.jpg
2. Musée des Arts et Métiers, Paris. (Picture by Roby, CC BY-SA 2.0 be)https://commons.wikimedia.org/w/index.php?curid=220593
3. Picture by Joao Luiz Musa; Marcelo Breda Mourao, Ricardo Tilklan, Public Domainhttps://commons.wikimedia.org/w/index.php?curid=9845344
4. Three F111 at different swept wing configurations—Picture by Jason Baker (Australia), CC-BY-2.0https://c ommons.wikimedia.org/wiki/File:Three_F-111s_with_different_wing_configurations.jpg