"I knew it was too good to be true,
Things between me and you were just going too smooth,
You tell me you're leaving,
You're going away, You're joining the airforce and you're sorry but you can't stay,"

Add a period at the end of "stay", I just felt like there were too many pauses going on. This was an alright opening, it described the scene for the reader.

"But i need you so much,
I need you here with me,
Isn't that enough for you to want to be here with me?"

Delete the "but" and capitalize your "i".

I think it will read better that way..

I also like the question added on, you think, won't that make you stay, please?

""Please dont go" is in the message i sent,
how was i supposed to know that you could never be kept?"

"dont" should be "don't".

I don't understand the second line, he could never be kept?

"I watch you bored the plane,
You look back at me,
Tears fill my eyes,
you say "dont ever forget me"
How could i?
because as you turn away,
My heart it begins..
It begins to break"

"bored" should be "board".

You definitly showed the heartbreak in your lines but I was expecting more emotion and more images of him leaving and kissing your hair, or something like that.

Good poem still, very touching and sad.

God bless you and Merry Christmas!

~MaryAnne