It is such a routine part of flying that it’s safe to say very few people listen: the preflight check when the flight attendant gives the speech on safety.

On Tuesday, a Southwest Airlines flight got into trouble when a engine exploded at altitude. A window in the cabin of the plane was shattered and the cabin pressure was lost. Just as the flight attendant always says, the oxygen masks dropped from an overhead compartment. Social media images showed passengers in the cabin, many of whom were wearing the masks incorrectly. Perhaps it’s helpful here to remember what the flight attendant always says:

“In the event of a decompression, an oxygen mask will automatically appear in front of you. To start the flow of oxygen, pull the mask towards you. Place it firmly over your nose and mouth, secure the elastic band behind your head, and breathe normally. Although the bag does not inflate, oxygen is flowing to the mask. If you are travelling with a child or someone who requires assistance, secure your mask on first, and then assist the other person. Keep your mask on until a uniformed crew member advises you to remove it.”

Yes, firmly over your nose and mouth. On Tuesday, videos show, people grabbed the masks and most put them over their mouths, but not their noses.