Critical fuel shortages for commercial flights at airports across Japan have led to difficulties in increasing the number of international flights and adding new routes, industry and government sources said Saturday. A surge in demand for flights due to increasing inbound tourism has outpaced the supply capacity of petroleum refiners, with the issue further compounded by labor shortages in the distribution phase. With the problem threatening to dampen efforts to revitalize regional economies through international tourism ahead of the peak summer holiday season, relevant government ministries a…