First let me ask if you hold this world to be a better place than heaven?
You ask me about a 20 year old, not a child. At a certain point in life a person becomes accountable before God. I would guess that a 20 year old pilot is old enough to have chosen or rejected Christ as their Lord and savior long before they were shot down over Vietnam.
Even if he did not, he was old enough to have understood good or evil, and thus be accountable to God for his choices in life. It is not a tragedy to die young if they knew Christ. What is a tragedy, is to live a full long life and never know Christ. Than they will be lost for eternity.
Think about that.. Eternity is a very, very, very long time. Even if you live to be 120, that is a very, very, very short time. We speak in terms of men, but we must understand things in the eyes of an everlasting eternal God.
However, my quote you took was for children who have yet to even understand what good or evil is when they had died. As a rule, children to young to be accountable are spared a long life of may miseries and instead get a pass to go straight to heaven. (as a rule, I am sure there are exceptions, but only God knows what those exceptions would be.)
I often times wish I could have been saved the grief of my many years of life in this world, and instead been granted a free pass to eternity without the pain I have suffered.
Wait a minute...you are saying that the guys who were shot down and killed had rejected Christ... I do believe that is a deductive leap that only a fool would make..... You are starting to make a fool of yourself with statements like that.... Probably need to save yourself and shut up...or as the old saying goes...better to appear a fool than open your mouth and remove all doubt!
One other thing.
The age of accountability will vary between each individual.
What one person understands and is able to accept at one age may not be that same as others.
I know 12 year olds who are very knowledgeable and should be held accountable. I also know of 18 year olds who are clueless.
Ultimately God knows the heart and what one understands about good and evil.
Ultimately, every knee shall bow, and every tongue will confess that He is Lord.
The question comes from what they knew, understood, and whether they accepted or rejected Him when given the chance while alive in this world.