What's the biggest FAIL you've suffered at work? Maybe you accidentally put aluminum foil in the microwave . . . maybe you pushed "Reply All" inadvertently . . . or maybe you've been mistakenly calling Charlotte "Scarlet" for six months.

A Delta flight attendant made a pretty big mistake during a flight last Saturday, when he accidentally DEPLOYED THE EMERGENCY SLIDE.

The plane was still at the gate at the time . . . thankfully . . . but you can't just deflate it, repack it, and go. It's a very complicated process, and reports say it'll probably cost the airline between $50,000 and $70,000.

The flight was supposed to go from Pittsburgh to Salt Lake City . . . but it was canceled and passengers had to be put on later flights, into the next day.

One passenger said the flight attendant did apologize to the travelers. He told them he had 26 years of experience and this has never happened before.

It sounds like he just did something wrong when securing the door . . . or did things in the wrong order . . . and triggered the slide.

Obviously, when there IS a problem you want the slide to deploy immediately . . . so there isn't an "are you sure?" feature. It's on the flight attendants to make sure they follow a specific "cross-check" protocol.

Sadly, the passengers were NOT offered the chance to use the slide when they deplaned.

Read More HERE, HERE