The Solar Impulse team says the flights to Belgium and France are a big challenge because the plane will need to navigate across international air traffic networks. The single-seater prototype with the wingspan of a Boeing 777 made its 2009 maiden flight in Switzerland and further tests have all taken place there. Pilot Andre Borschberg said Thursday the success of the first cross-border flights depends on the team receiving authorization from national authorities. The team says it will ready the plane from May 2 and take off to Brussels when weather conditions are right. The plane is expected at the 49th International Paris Air Show from June 20-26.