Numerous passengers on the US flight where a woman was almost sucked out of the plane were wearing their oxygen masks wrong, says a retired flight attendant.

New Mexico's Jennifer Riordan, 43, died after nearly being completely sucked out of a Southwest Airlines flight from New York to Dallas.

The Boeing 737's engine exploded during the flight, smashing the jet's window and damaging the fuselage.

Travellers said fellow passengers dragged Riordan – who has two children - back in as the sudden decompression of the cabin pulled her part way through the smashed window.

Seven other passengers were injured in what was the first passenger fatality involving a US airline since 2009.

Oxygen masks dropped from the cabin after the explosion and a passenger shared a photo on social media of the travellers wearing the breathing aids.

TV show host and former flight attendant Bobby Laurie then took to Twitter to remind people how to correctly wear the masks.

"Cover your nose and mouth," said Laurie, who also claimed nearly everyone pictured in the photo was wearing their mask wrong.

PEOPLE: Listen to your flight attendants! ALMOST EVERYONE in this photo from @SouthwestAir #SWA1380 today is wearing their mask WRONG. Put down the phone, stop with the selfies.. and LISTEN. **Cover your NOSE & MOUTH. #crewlife #psa #listen #travel #news #wn1380 pic.twitter.com/4b14lZulGm

— Bobby Laurie (@BobbyLaurie) April 17, 2018

According to an article published on Business Insider, failing to attach an oxygen mask correctly is dangerous.

"At altitudes above 15,000 feet, people struggle to breathe and keep enough oxygen in their blood. They can lose consciousness within minutes – a condition called hypoxia," Business Insider reported.

Symptoms of this condition nausea, apprehension, tunnel vision, headaches, fatigue and mental confusion among others.

Interestingly, it actually the lack of pressure that makes it dangerous not to put the oxygen mask over both your mouth and nose.

"Insufficient pressure lowers air density, thereby decreasing the amount of available oxygen," Business Insider said.

If you don't cover both your nose and mouth, you may struggle to get enough oxygen in your bloodstream, which in turn may induce unconsciousness.

"Passengers who are passed out won't be able to evacuate," Business Insider said.

"And if there's any kind of fire or smoke condition, an unconscious neighbour slumped in an aisle could mean the difference between life and death. That's why masks are designed to deploy immediately."