Passengers on a Southwest Airlines flight from Denver were terrified this weekend when the oxygen masks dropped from the ceiling, and the plane quickly landed at Dallas Love Field.

It's apparently the third emergency landing on a Southwest plane in the last month, and it's still not clear what caused the "pressurization issue in flight,"as the airline apparently called it. But this time, there's some really good news. 

First, of course, there's the fact that nobody was injured--nothing more than four passengers who reported earaches, apparently from the rapid descent.

But there's also something that eagle eyed social media followers noticed when the inevitable parade of photographs started popping up on Facebook and Twitter.

It's that barely a month after flight crew and other observers called out passengers aboard Southwest Flight 1380 for not using their oxygen masks correctly, the images from this flight show something different.

Passengers sitting still--and wearing the masks correctly, so that it covers both the nose and mouth.

All, apparently, without being given much guidance by the flight crew.

"I had no idea what was going on or what the outcome was going to be," passenger Glen Eichelberger told CBS 11 in Dallas, adding, "I didn't know if we were were going to make it or not. There was no communication what so ever from the flight attendants or from the cockpit as far whether we were in mortal danger."

Again: disconcerting to say the least. You can certainly imagine that if you're on a flight where the masks drop, you'd like to hear a reassuring word or two from the flight crew as you descend.

But still, using the masks correctly is important. Without them, if the cabin loses pressure you only have about 30 seconds of breathable air, if the plane doesn't descend quickly enough.

With masks, you can instead hold on for between 12 and 20 minutes--more than long enough for pilots to get the plane below 10,000 feet, where the air is breathable.

So, yes, Southwest is going through a rough time, with three headline-grabbing incidents aboard its flights in the last month.

But if there's a bright side about all the incidents and coverage, maybe it's this. Millions of people have seen these articles and watched the videos showing what not to do in the event of an emergency.

And so now, there are now a lot fewer people who don't know how to put on and use an airplane oxygen mask in a hurry. That knowledge could, one day, prevent another real tragedy.