There Are Usually Two Announcements
The first (I must still have been dreaming about my upcoming travel stops) I hadn’t noticed, is typically something like “arm doors and cross check.” To board an airplane the doors must obviously be open. However, before they’re opened and unlocked, the inflatable slides we ignore listening about prior to take off must be disconnected from the door. That prevents the slide from popping out when the doors are opened. The first cross-check announcement is a reminder before liftoff for the flight attendants to properly seal the doors and reattach the slides in case they’re needed.
“Cross-check complete” means just that. Flight attendants have verified that the doors on both sides of the aircraft are properly locked and their evacuation slides ready in case of an emergency.
What Would Happen Someone Forgets A Cross Check?
Something like this, when the airplane door is opened. Imagine that happening after pulling up to the airport gate.
So once you land, another cross-check is done to make sure the safety slides are properly disengaged from the doors. Now, next time you’re daydreaming before your next flight, you’ll know those flight attendants aren’t talking about ninja training. Rather, they’re making sure the evacuation slides are ready before you’re in the air and don’t deploy right before you deplane.