A Qantas A380 plane bound for Melbourne plunged for about 10 seconds mid-air because of a vortex created by another aircraft flying above it.
Passengers on board flight QF94, which departed Los Angeles late on Sunday local time, experienced a sudden turbulence "jolt" when another A380 bound for Sydney flew above and ahead of it, the airline said in a statement.
Qantas fleet safety Captain Debbie Slade said "wake turbulence" from the A380 flying above was to blame.
Wake turbulence forms behind an aircraft as it passes through the air, and air traffic control requires more spacing behind larger jets like the A380 to avoid it.
"We understand that any sudden turbulence can be a jolt for passengers but aircraft are designed to handle it safely," Captain Slade said in a statement on Thursday.
The two aircraft were separated by 20 nautical miles and 1000 feet in altitude.
No passengers were injured and there was no aircraft damage from the incident, a Qantas spokesman said.
Australian television presenter Eddie McGuire, who was on board the flight, said the incident lasted about 10 seconds.
"It did have that feel of, you know when you go over the top of a rollercoaster and you just get a little bit of a feeling," he told the Nine Network.
"But it steadied up after about 10 seconds."
The Australian Transport Safety Bureau was notified of the incident on Thursday morning, with the bureau saying there was no need to be notified earlier because the incident didn't affect the safety of the aircraft.
The ATSB won't be investigating the incident.