In order to make solar flights between continents possible, infrastructure has to be in place. Intercontinental air traffic would definitely require one or more stops with today´s battery capacity.
I imagine a
global network of solar- wind- and wave- based energy power plants placed underneath the air traffic channels between the continents. With landing spots at sea, airplanes in need of fuel (or should we say power) could make a stop to recharge the batteries with fast- charging cables.
The power plants can work independently, or be used by both ships and aircrafts. Domestic or international flights over land would recharge by using existing airports. They can produce their own renewable energy such as solar, wind or geothermal energy.
That being said, there is a little way to go before full- scale aircrafts are commercially available. The best would of course be solar panels so effective that landing would be unnecessary. Even more so because solar energy is more efficient at high altitudes, since the photons in sunlight don´t have to go through the atmosphere before they hit the solar panel. Going directly into the solar cells, a larger percentage of the photons are generating electricity.
Let´s find a way of utilizing this energy more efficiently! I´m on my way, just need a little more advanced education first...