Both destinations are served by Chhatrapati Shivaji International Airport (BOM). Since there's no flight route between them, the best way to travel is by road.
Mumbai
Fly to Chhatrapati Shivaji International Airport (BOM), then travel by road to Mumbai. Taxis, buses, and private cabs are available from the airport.
Boisar
Fly to Mumbai (BOM), then travel by road to Boisar. Local transport options include taxis, auto-rickshaws, and state buses.