A plane that existed more on paper than in actuality. Produced in extremely small numbers or prototype levels.
The J-8II PP is an unicorn airplane because it was an American upgrade package to the J-8II but never delivered due to sanctions around Tiananmen Square.
When someone cuts themselves off from the world by not logging on to Facebook or checking their cell phones. Usually occurs after a breakup or a rough work week.
Derived from the cell phone setting of the same name in which incoming messages or phone calls cannot be received.
"Dan won't answer your calls. He's in airplane mode."
"Sarah went into airplane mode for three days after Charlie dumped her."