Graves' disease is an immune system disorder that results in the overproduction of thyroid hormones (hyperthyroidism). Although a number of disorders may result in hyperthyroidism, Graves' disease is a common cause.
Flight time from LAX to JFK is 5 hours 6 minutes. Delta Air Lines is one of the direct flight which takes 5 hours 6 minutes to travel from Los Angeles International Airport (LAX) to John F Kennedy International Airport (JFK). Flight time from New York to Los Angeles (all airports).
Dallas Fort Worth to Sydney is around 17 hours, and there are some direct flights on that route. However, most routes go via LAX, so you are flying across the US before you actually start for Australia. LAX to Sydney is around 15 hours, NYC to LAX is around 5 hours. By the time you have dealt with layovers and the security circus, NYC to Sydney will be about 22 - 24 hours.