PHOTO: All Nippon Airways (ANA) jetliners taxi at the Tokyo International airport.

What goes up, must come down.  Very quickly.  Especially if you press the wrong button.

That was the lesson learned the hard way by a Japanese pilot who nearly tipped a plane full of 117 passengers last month on a flight from Naha, on the southern island of Okinawa, to Tokyo.

Two more lessons learned from the near-catastrophic incident?  Don’t use the restroom on a flight, and always make sure the pilot is in command.

The 38-year-old co-pilot at the helm of the All Nippon Airways (ANA) flight hit a wrong button while trying to push the door’s unlock button to let the captain back into the cockpit after he stepped out to use the restroom.

Instead of pressing “unlock,” the co-pilot hit the rudder trim controls, a mistake that tipped the Boeing 737-700 more than 130 degrees to the left, and sent it plunging 6,234 feet in 30 seconds, all while flying at a height of 41,000 feet.

Though the incident occurred Sept. 6, it was just revealed by the airline Wednesday, hours after the airline debuted its new-generation Boeing Co. 787 “Dreamliner” jets.  Shin Nagase, a senior executive vice president at ANA, bowed deeply in front of TV cameras at a news conference to apologize for the trouble caused by the incident.

Computer images released by the Japan Transport Safety Board show the plane nearly turning upside down.  The flight’s passengers, luckily, did not seem to realize the gravity of the situation, since it was already dark outside when the incident occurred, around 10:50 pm.

Two flight attendants were slightly injured, and six passengers became airsick or reported neck pains aboard the flight, which later landed safely in Tokyo.

Four senior ANA officials have been reprimanded by the airline as a result of the incident.  The Japan Transport Safety Board has also launched its own, independent investigation.