Your plane is on fire. You can see smoke billowing outside the windows. Flight attendants are screaming to evacuate. So you unbuckle your seat belt, stand up, open the overhead compartment and make sure you grab that nice piece of luggage you brought with you.

I mean, you can’t possibly let it burn!

Wait, what?

That scenario might seem like something straight out of a “How NOT to Evacuate a Burning Airplane” guide, but it is very real. The terrifying scene unfolded on a Las Vegas tarmac when the engine of a British Airways Boeing 777-200 burst into flames.

Instead of running for their lives, passengers did something that is unconscionable in the eyes of flight attendants: They grabbed their bags.

[‘I’m finished flying,’ British Airways hero pilot says after Las Vegas fire]

And not just the purses beneath their seats (though, you should leave those too). Some people could be clearly seen evacuating the plane carrying roller suitcases that had been retrieved from the compartments overhead.

The danger is obvious, say flight attendants.

With a plane on fire — or, really, in any emergency situation — flight attendants are trained to help passengers evacuate as quickly as possible.

Specifically, they want to clear the plane within 90 seconds.

That’s impossible if even a few people on a full plane stop to grab their bags.

An engine fire is particularly dangerous. Luckily, British Airways Flight 2276 was far from full, allowing passengers to evacuate more quickly. And the fire never pierced the fuel tank or the cabin.

But it easily could have been worse.

[Quick action averts disaster as flames and smoke engulf London-bound jetliner]

“Absolutely selfish and pathetic,” commented one flight attendant who was not authorized by his airline to be quoted. “You are hindering the person on the window side from quickly evacuating. And what if they panicked and trampled you to death?

“Leave it! Not worth your life, it can be replaced.”

The fears go beyond just the time it takes for people to evacuate if they are also, perplexingly, trying to bring their bags with them. What if their purse strap gets caught on the arm rest? Or the roller board suitcase punctures the massive plastic slide that is virtually the only hope of getting to safety?

And finally, flight attendants are understandably concerned about their own safety.

They undergo mandatory training on how to help passengers save their own lives should something go wrong on an airplane. They and the pilots are also required to be the last people to exit the plane in an emergency.

Evacuating a plane in 90 seconds isn’t just a matter of pride for those who are able to accomplish it; it’s a matter of life or death.

According to Sara Nelson, international president of the Association of Flight Attendants, passengers should heed the commands of flight attendants during an emergency — and leave their bags on the plane.

“We expect the [National Transportation Safety Board] investigation will show that the bags slowed the evacuation and may even have caused some of the injuries,” Nelson said in a statement.

In the case of the fateful Flight 2276, all passengers and crew survived. But according to the Associated Press, 27 people were hospitalized with minor injuries — including all 13 members of the flight crew.