An unpredictable person who has terrible organisational skills when it comes to thier own life. They cannot be relied on to make plans or be involved in activities that require any kind of careful preparation.
Tony: "Hey Hank, is Matt bringing the birthday cake for the surprise party?"
Hank: "Nah, i dont trust him after he forgot it last time. He's a total flight risk!"
For a person that isn't reliable, or trustworthy enough.
You cannot coexist with a person like this, cause simply he/she will make you regret it cause he/she sounds like ticking time bomb of unfortunate events.
e.x.
Person A:
I need some serious leisure time. It feels like I'm working non stop. You wanna go somewhere with me this summer?
Person B: You can't keep a dollar in your wallet and you want to go vacations with me? Jesus, what a flight risk!
When you're playing the childhood game of Airplane and the person in the air is getting railed so hard by the third party that they fall over and yell "bombs away!!"
Damn, John. You need to start doing more leg lifts. You let Amanda fall into the flight risk because I was nailing her so hard. She hit her face on the ground.