Complex sentence: One reason for building this airport in this particular location is that locals and tourists will not have to rely on the severely congested airports of the Tokyo region, so any flights that bypass that region will help overall air traffic, including direct international flights.
Split into simpler sentences: One reason for building this airport in this particular location is that locals and tourists will not have to rely on the severely congested airports of the Tokyo region. Any flights that bypass the Tokyo region will help overall air traffic, including direct international flights.