To abort or not to abort, this is a real question. But, only when it comes to aborting a mission voluntarily. Involuntary mission abortion (The enemy made me do it) is spelled out closely in the rules in 2.6.3 Engagement vs Contact. But what about those times when it just don't feel right (and for the USN that means at night). Can you voluntarily abort a mission before the enemy gives you no choice in the matter? I know you can, but the rules are generally silent upon any restrictions.
Here is when I believe you can (and should) voluntarily abort missions(s) and I expect Dave to chime in and say if I'm right/wrong or just deluded.
1. Prior to any contact die rolls, when upon reflection you have decided that sortieing that mission (like a USN sweep from Tarakan on turn 1) was a really bad idea to begin with.
2. After contact die rolls, but possibly before you've gotten stuck in the soup and have actually seen something to shoot at; but you don't like it at all. This would be a USN sortie when you realize, man oh man is it dark, the sun had set and without flash-less powder it is not going to go well for you.
3. Any time (if you are Allied) and the situation you see is not promising. Make smoke and run, letting those irreplaceable ships of yours live to fight another day in a situation when the Japanese should have run instead.
OK, OK; what about the Japanese. What about them? The WAF ( Western Attack Force) should never (given average competence) face a situation in which it needs to abort. The EAF (Eastern Attack Force) is another story. The EAF has 16 convoy missions available to capture 13 objectives. Sounds like plenty and it is if the WAF transfers all its Takao class cruisers; the 4th, 6th and 8th destroyer divisions as well an AV and 10 transports to the EAF on game turn 1.
Never the less due to bad mission choices or just bad luck you are going to find yourself in situations where going banzai is just going to cost you your escort as well as your transports. So, in those situations, upon sober reflection, make smoke, have the escorts run and abandon the transports to their fate. But remember, you can only do this three times. Do it a fourth time and you lose. So like Elmer Fudd said; "Be very careful" in deciding to abort.