The spacing (called separation in aviation) is based on aircraft weight (which is similar to size). A heavy can take off following another heavy sooner than a

The spacing (called separation in aviation) is based on aircraft weight (which is similar to size). A heavy can take off following another heavy sooner than a medium or light can take off following another heavy. This means you can increase capacity by substituting bigger aircraft for smaller ones. Some separation details are listed at http://www.skybrary.aero/index.php/Mitigation_of_Wake_Turbulence_Hazard http://www.skybrary.aero/index.php/Mitigation_of_Wake_Turbul... Gate spacing is an issue, but it is considerably easier to build more ramps and terminals, or update existing ones. The next generation 777 has folding wingtips for its longer wings so they still fit in code E spaces and taxiways. The largest is code F where a plane must fit in an 80 metre by 80 metre box. The A380 wingspan coincidentally is 79.75 metres. Landing fees at these airports are typically based on the aircraft weight, so airports are happy to have more passengers. They get more revenue, there is more incentive for connecting flights, there is more revenue for retail, parking etc. Bigger planes with more passengers are generally a nice problem for them to have.