The way the scam works is that they send you a check for more than the value
of the aircraft.

The check is a real check drawn on a real account that does not belong to
them. They have you pass the overpayment to their 'shipping agent'. They
don't care if you deliver the plane or not. The money sent to the shipping
agent disappears.

Come the end of the month the real account owner notices the bogus check and
after all the dust settles you owe them the total value of the check. You
still have the plane so after you refund the payment you are just out the
money you sent on to the shipping agent.