Mid-air mechanical issues forced back two Qantas flights after they left Sydney this afternoon, with one having to dump fuel over the ocean before landing.
A flight to Dallas turned around after the flaps on the Airbus A380 were unable to retract, a statement from Qantas said.
The plane circled for 35 minutes and had to dump fuel but has now landed and will be inspected by engineers.
Another flight to Johannesburg returned to Sydney this afternoon after a pane of glass on the windscreen cracked.
However, aircraft windscreens have three layers and only the outer pane had cracked so the integrity of the aircraft was not compromised.
The flight was safe to continue to Johannesburg but the captain made the decision to return to Sydney.
Qantas said it was working to accommodate affected passengers or offer them transport home before replacement services were organised.