(Reuters) - Australian flag carrier Qantas has had to delay several flights on the Sydney-Johannesburg route over the past few weeks on the U.S. government's advice regarding the re-entry of SpaceX rockets over a part of the southern Indian Ocean, the airline said on Tuesday.

The delays of up to six hours were caused due to last-minute changes in coordinates for the location and timing of re-entry of rockets from Elon Musk's space technology firm.

"While we try to make any changes to our schedule in advance, the timing of recent launches have moved around at late notice which has meant we've had to delay some flights just prior to departure," said Ben Holland, the head of Qantas's operations centre.

"We're in contact with SpaceX to see if they can refine the areas and time windows for the rocket re-entries to minimise future disruption," Holland added.

SpaceX did not immediately respond to a request for comment.

(Reporting by Aaditya Govind Rao in Bengaluru; Editing by Mrigank Dhaniwala)