It’s hard to stay cool under pressure.

Passengers on a Qantas flight were reportedly forced to evacuate the plane after it filled with smoke. One traveler took to social media and claimed that the pilot screamed at everyone to evacuate.

The flight turned around and landed back at Sydney airport shortly after takeoff, the Guardian reports. Instead of flying to their original destination of Perth, passengers instead were told to leave the plane via the emergency slides.

The decision to turn around was made after the cabin filled with smoke, which the airline says was due to a “hydraulic issue.”

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A woman claiming to be a passenger on the flight shared her experience on Twitter.

“Just had to evacuate my flight to Perth after engineering issues,” wrote Ally Kemp. “Everyone had to exit the plane via slide onto Sydney tarmac after the cabin filled with smoke and the captain screamed evacuate. Terrifying.”

Another passenger on the flight, Niamh Champion, shared a similar story. According to The Sun, she said, “And next thing he (pilot) goes, 'evacuate, evacuate, evacuate', like in a calm but firm, loud voice. So instantly everyone jumps off and they're thinking, 'Oh my God. I thought there was smoke, or a fire or, you know, something was happening.’”

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After explaining that she was close to the back of the plane when the incident occurred, she continued, “The hostess opened the door, bang, the chute comes down and everyone starts rushing into the aisle.”

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A statement released by Qantas explained, "Qantas engineers are working to determine the cause of a hydraulic fluid leak on board one of its Airbus A330s, which resulted in an evacuation of the aircraft at Sydney Airport. QF575 departed Sydney for Perth at 8:45 a.m. this morning. Approximately 20 minutes into the flight, the Captain received a cockpit alert for one of three hydraulic systems on the aircraft. The Captain elected to return to Sydney and the aircraft landed safely shortly afterward. No emergency was declared."

The statement continues to explain that while some passengers may have mistaken a haze that appeared in the cabin for smoke, there was no fire. It was likely caused by hydraulic fluid entering the air conditioning unit.

"Two passengers were treated for injuries sustained from using the slides and another passenger was taken to hospital as a precaution," the statement continues. "Some customers reported sore eyes and itchy throats."

Qantas Fleet Safety Captain Debbie Slade said: “We totally understand this would have been a very unusual and probably alarming experience for our customers, so we thank them for giving the crew their full cooperation. The crew did a great job of putting their training into action and following the procedures for a set of circumstances like this. We’ll investigate exactly what happened, including liaising with Airbus, before this aircraft is returned to service.”