In this reality, Charles Xavier became the Juggernaut who formed the X-Men. Thunderbird is a member of Charles Xavier's X-Men who serves as a police force that aids the mutants and persecutes the sapiens.
The total flight duration from Sydney, Australia to Boston, MA is 20 hours, 41 minutes. This assumes an average flight speed for a commercial airliner of 500 mph, which is equivalent to 805 km/h or 434 knots. It also adds an extra 30 minutes for take-off and landing. Your exact time may vary depending on wind speeds.
Flying to Australia is a long arduous experience. We know as we have flown from Europe to Australia and from the United States to Australia many times. The journey from Los Angeles to Sydney is a nonstop flight and typically takes around 14 to 15 hours.