Complex sentence: Since it is currently only a proposal, construction of neither the terminal nor the APM line has begun, however, is scheduled to be completed after the completion of the Maynard Holbrook Jackson, Jr. International Terminal.
Split into simpler sentences: Since it is currently only a proposal, construction of neither the terminal nor the APM line has begun. If it is built, it will be completed after the completion of the Maynard Holbrook Jackson, Jr. International Terminal.