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.
Travelling By Air: If you were in a plane say a Boeing 707 and maintained an average cruise speed of 450 mph (724.1 kmh) over the course of your it would take you around 1.1 hours to get from Boston to Philadelphia.