It'll never fly

It'll never fly.

Fig. It will never work!; It will never be approved! (Refers originally to an evaluation of an unlikely-looking aircraft of some type.) l have read your report and studied your proposal. It'll never fly. Your design for a new electric automobile is interesting, but it'll never fly!
See also: fly, never

It'll never fly.

  (American)
something that you say when you think an idea will not be successful He sent me a movie script but it'll never fly - it's just too unbelievable.
See also: fly, never
References in periodicals archive ?
IT'LL NEVER FLY Wingtip embedded in tailplane elevators
In terms of assembly, you can hack this together for a prototype, but it'll never fly in a production environment.
It'll never fly with that ridiculous name Fort Fadeaways.