Bizarre footage has emerged of fog filling the cabin of a Jetstar flight from Bali — but the airline insists there was nothing to worry about.

The dramatic video was posted on YouTube earlier this month, and shows the plane cabin filling with fog.

A flight attendant can be heard reassuring passengers while the video is filmed.

“Ladies and gentlemen, for those of you who may be a little concerned about the haze through the cabin, this is just due to our air conditioning systems,” she said.

“It’s quite similar to, in winter, when you are outside and you breathe out some warm air into the cooler air, it just produces some condensation.

“It should clear once we reach a higher altitude and the outside external temperature drops.”

A Jetstar spokeswoman reportedly confirmed that the fog was formed due to condensation in the cabin.

“When air conditioning is switched on, this condensation can create a ‘fogging effect’ for a couple of minutes until the moisture dissipates,” the spokeswoman said.

“In this case, the condensation was more than you might commonly see given the temperature differences.”