English Grammar - Verbs - Simple Future

The Simple Future is expressed in a number of ways. The most common are with "will" and "be going to".
Examples:We will go to see you in some days.
I am going to see David tomorrow.
Both "will" and "be going to" can be used interchangeably in some cases such as predictions and guesses.
We use "will" to express a voluntary action which is one the speaker offers to do for someone else. Often we use "will" to respond to someone else's complaint or request for help.
We use "be going to" to say something is going to happen when it has already been planned.
Sometimes future time can be expressed with either the present or present progressive tense. In such cases, time words must be expressed or clearly implied.
Example:
I fly to New York tomorrow.