Try and make a solar powered fixed wing aircraft fly at 43 mph while being 1 foot wide and reserving 25% of it&#x27;s weight for cargo and keeping it in the air for 36 hours. You have 45 kW &#x2F; (200 ^ 2) = 1.1 watts peak solar output to work with.<p>The issue with overly large wings is mechanical stress let&#x27;s try and get around that.<p>&lt;This is a dumb design&gt; As a thought experiment, take 3 Solar impulse aircraft fly them next to each other with a simple non weight baring cable to share power between them.  The outer two can clearly provide more power than they need and supply that extra power to the center one. Now the center one has extra power for &#x27;free&#x27;. So, it can have a higher angle of attack and more weight.<p>As to scaling birds, a Quetzalcoatlus had a wing span of 9 to 12 meters.  That&#x27;s huge for a land animal. <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Quetzalcoatlus" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Quetzalcoatlus</a>  Birds are limited by biology not so much aerodynamic issues.