The greater question is what is justice?
Is Joe Keller a tragic hero? I don't think so since he is not a man of great stature, not a king or leader or hero, so who is he? Is Joe a likable guy? Yes, but he was man who makes a grave error. He does not accept responsibility for his actions but rather blames his partner. Is this the action of an honorable man? I think not. What Joe is is a human being. When he is confronted with the truth he justifies his actions. Everybody who manufactured for the war effort did similar things therefore in his mind he was not guilty and saw no reason why he should have to go to prison. It was terrible that 21 men died as a result of his decision but it was wartime.
Kate states that if she were to admit the truth of Larry's death, then Joe was to blame. Ironically, he was since Larry could not live with the shame of Joe's action and crashed his plane.
Is the ending acceptable/satisfying? It is the only possible ending once the truth is out. Joe stated earlier that he would kill himself rather than go to prison.
It seems to me that Miller was influenced by Ibsen where we see recognisable human beings struggling with their realities. And as in Ibsen the ending is not neat or tidy. What happens to Kate now that she has been forced to face the truth? What will happen with Chris and Ann since they too have been forced to face the truth? Life goes on and there are no easy answers.
In my opinion, the ending of "All My Sons" is not satisfying; it's hard to be satisfied upon seeing a mostly decent fellow kill himself. The ending is, however, tragic.
Tragedy has been defined as follows: A drama or literary work in which the main character is brought to ruin or suffers extreme sorrow, especially as a consequence of a tragic flaw, moral weakness, or inability to cope with unfavorable circumstances (see link below).
Joe Keller has an essential flaw: he is willing to lie in order to provide a respectable life for his family. He manages to get away with his lies for a few years, but eventually it brings him and his two sons to ruin.
"All My Sons" is a classic Greek tragedy in a modern setting.