Become a Plane and Fly invalid code issue (Image via Roblox) Codes for Become a Plane and Fly have an expiration date, so they won’t work once that time is up. Errors can also happen if you ...

Open Build a Plane Tycoon on Roblox. Click on the ‘Codes’ icon located on the left side of the game. Copy and paste the code from this guide into the ‘Enter the code here’ textbox.