Renee Kenyon, 21, was among 212 passengers on flight QF74 from San Francisco on Monday when the aircraft's fourth engine failed.

"We were in the air for about 20 minutes, still on the ascent, and then I heard this boom. The plane shifted to the side then dropped a little bit. It was not turbulence," Ms Kenyon said.

"Everyone was gasping. I looked around and saw sparks and flames through the windows on the right hand side. The whole plane was shaking.

"You could smell a burning smell inside."

Ms Kenyon said a group of men seated behind her were praying for their lives, while girls seated beside the windows were crying.

But she was not frightened during the mid-air emergency and described it as surreal.

"When the pilot came over (the speakers) and said the plane was dumping fuel and we had to go back I was mad. I wanted to go home," Ms Kenyon said.

"I was not scared."

The Boeing 747-400 was about 150 kilometres into the flight to Sydney when it turned back to San Francisco.

Ms Kenyon, a bar attendant, said she waited on the plane when it was on the tarmac for almost four hours while the crew took passengers off individually.

Once she was escorted off, Ms Kenyon logged onto Facebook to try and contact her mother, Helen Kenyon, who eventually spoke to her on the telephone at 3.30am.

Helen said she did not panic until she saw the morning news.

Megan Kenyon, 23, got a text message from her sister saying: "Hope someone reads this ASAP. Don't panic, I am okay".

Ms Kenyon arrived in Melbourne yesterday morningntsThursdaynte after taking another flight out of America.

She said the Qantas crew handled the emergency really well and helped people feel comfortable.

She said the emergency had not affected her and she would get on an aircraft again.

Ms Kenyon had been on a two-week trip to Canada to visit her cousin, Los Angeles and San Francisco.