Is this what you're looking for...?
Oh I have slipped the surly bonds of earth
And dance the clouds on laughter silvered wings.
Upward I climb amidst the tumbling mirth,
Of sun split clouds, doing a hundred things
You've never dreamed of. Wheeled and soared and swung,
High in the sunlit silence, hovering there
I chase the shouting winds along,
And hurl my eager craft through footless halls of air.
Up, up, the long, delirious, burning blue
I top the wind swept heights with easy grace
Where never lark or ever eagle flew
And whilst, my silent lifting mind I trod
The high untrespassed sanctity of space
Reach out my hand, and touch the face of God
By John Gillespie Magee. World War 1 Fighter pilot who died
In aerial combat aged 18 years.
A google search found it fairly quickly, though I only checked the first half dozen or so links provided. If this is not it, perhaps there's something else I didn't get to.
Sorry to hear about your grandfather. Was this special to him?