On the Fly means “while in the process.” Particularly, modifying something during the process of a whole.

In Product Design, On the Fly concept pertains to the capability of the Genesis of a thing during a process.

Consider a simple form which asks for the type of industry you’re working in. Generally, the following are the possible interactions that you might encounter:

• if there’s a list already, you only have to identify which item applies to you
• if there’s no list available, you have to input the item that applies to you
• a combination of the two and with the On the Fly concept applied, you could input the item that is not on the list and have it saved in the system for later retrieval

The On the Fly concept gives users freedom to create items to use in the process while being in the process and not create the item separately from the process.