Mention of a code of conduct between pilots reminds me of the great story of the Charlie Brown and Franz Stigler incident. Great story.
What do you call dismounted armor crew?
Infantry.
The (IMHO fatuous) “chivalry” of air officers never seemed to apply to armor. While a tanker would be the last to admit they’re not meaningfully* different than a dogface if they don’t have their vehicle, it’s still true.
*Granted, they’re not equipped the same – smaller personal weapons, different helmet and body armor, etc. But if you shoot at them they’ll take cover and shoot back with whatever they have, so infantry.
It depends on the circumstances to some degree, of course, but it is perfectly clear that a pilot bailing out of an aircraft because it was destroyed is helpless and out of the fight.
Since WWII, a protocol to the Geneva Conventions specifically protects pilots ejecting from an aircraft. There is no such protection for tankers.
The laws of war were perhaps respected on the Western front from 1939 to 1941. Otherwise, not so much.
That also varied. There was some idea of not firing on crews abandoning tanks in the ‘war without hate’ between British and Germans in North Africa. As noted that isn’t so different from tanks coming upon infantry in the desert, but in North Africa infantry would generally surrender if caught in the open by tanks or tanks broke into their wired/mined positions, if without their own anti-tank gun support, since infantry then generally lacked effective man portable AT weapons which appeared later in the war. And the general ethos was not fight to the death on either side.
But in most of WWII most places sure crews abandoning tanks were fired on, and it surely happened in North Africa. Besides which on a confused land battlefield it wouldn’t always be clear anyway what caused casualties of dismounted tank crews.
Back to fighter combat, there was a debate when exactly the enemy air man was no longer fair game. It’s relatively unusual to see USAAF fighter accounts admitting gunning German pilots in their parachutes, more cases where it’s stated that units felt it legitimate to keep firing as the pilot bailed out before he was clear of his plane. The reason was what’s been stated, USAAF fighters were generally combating the Germans over Germany or Occupied Europe, a surviving German pilot could be back in action immediately with a new plane and the Allies had at least a general idea how much more plentiful new planes were for the Germans than well trained pilots esp by ca. 1944, though we understand that more exactly in hindsight. A downed US pilot was lost for the duration, except in rare cases he managed to escape from the occupied countries and very rare ones from Germany.
Again there though, accounts from the side of pilots shot down are clouded by uncertainty of how pilots were really killed.
It’s not just parachutes that this question comes up in.
In the WWII novel Run Silent, Run Deep, the captain of a US sub deliberately rams lifeboats of a ship commanded by a crafty and competent anti-submarine captain, in order to prevent him from getting another ship. This is portrayed as a questionable decision in the novel.
In real life, the captain of the USS Wahoo* was involved in an incident of machine gunning lifeboats, though the incident is shrouded in controversy.
*What a name for a ship, Yes, a “wahoo” is a type of fish, but so is sardine, minnow, and shrimp, but they never names subs after those fish. Wa-hoo!
The Geneva Convention didn’t take place until after WW2. To my knowledge, it prohibits the targeting of parachutists from an aircraft in distress, as distinct from paratroopers. Paratroops are fair targets whether they are deploying or bailing.
It would seem to me that a tank crew has the option of surrendering to the enemy, while a parachuting pilot would have a hard time signaling an intent to surrender.
That is not entirely correct.
The Third Geneva Convention, relating to treatment of prisoners, was adopted in 1929, and was effective for WWII prisoners. See: Heroes, Hogan. 
It does not specifically mention bail-out parachuting, though.
There is the story of a USAAF bomber sinking a German sub that was one the surface with rescued Allies on the deck.
Mt Father described his unit shooting at a Japanese pilot parachuting. He had been strafing them, and they were pretty angry.
That would be U-156, while the air crew did get credit for sinking her, she wasn’t actually sunk, only forced to dive(the difference was of course academic to the people sitting on her deck).
This was later known as the Laconia Incident.
I don’t mean to sound as if I’m picking on you; its human nature to want to see one’s own side in the best possible light, but the Pacific Theatre was infamous for the killing of those rendered hors de combat, not just the Japanese side. Not just shooting at parachuting pilots, but strafing lifeboats and machine gunning floating survivors from sunken ships was common practice on both sides of the war. For examples, American naval pilots spent some time strafing the survivors after sinking the battleship Yamato, from Russell Spurr’s A Glorious Way to Die:
From earlier in the war, in the aftermath of the Naval Battle of Guadalcanal on November 13, 1942, from Samuel Elliot Morrison’s History of US Naval Operations in World War II, volume 5:
I was gonna say that I remembered Alec Guinness’ character in Bridge on the River Kwai citing the Geneva Convention regarding his men’s treatment as POWs.
I’d imagine (and this is partly backed up) by what little I’ve read that a tanker or pilot might naturally view an enemy bailed-out tanker or pilot as either a gentlemanly comrade, or at least someone who was clearly out of the fight and harmless. But an infantryman, after being shot at from the sky or from behind armor and unable to respond, might see a bailed-out tanker or pilot as a chance to get some revenge.
This may or may not apply to WW II. I do volunteer work on the USS Midway museum with quite a few Vietnam era pilots. A recent event included both U. S. And North Vietnamese pilots. W/regard to them meeting above in the skies of NVN, both agreed they weren’t trying to kill their opposition. It wasn’t personal. All they were interested in doing was shooting down an enemy’s aircraft. Unfortunately for U. S. Pilots shot down, those on the ground felt differently of our pilots. Back to the aforementioned event, at one point one U. S. pilot realized the man sitting next to him was the Mig pilot who shot him down. What a moment.
I agree. When I was younger, the literature seemed filled with versions of the claim “the Japanese fought fanatically with no thought of surrender and had to be killed to the last man.”
But having read more widely, I have seen numerous claims that this was a two-way street – the much better-equipped Americans showed little mercy in the heat of battle. Once you think your enemy won’t surrender (or will hide a grenade in his clothes before surrendering), it would be easy to adopt a “kill 'em all” policy. It seems likely that a lot of the later-war battles in which Japanese casualties were nearly total might be a combination of Japanese ethos (whether “fanaticism,” duty, self-sacrifice, or simple fatalism) and American unwillingness to take prisoners in the first place (whether from racism, fear of being harmed, revenge/hatred, or simple habit, made possible by a material abundance in the machinery of war).
Surrender is always a difficult transaction on the battlefield, as the losing side is essentially asking the prevailing side to expose themselves to risk on their enemies’ behalf. It must be easier to roll a drum of gasoline into that tunnel, regardless of what the people inside are calling to you, than to go in there with a pistol in hand to investigate.
Also remember that as the war went on, the physical circumstances of the increasingly-asymmetric war made many Japanese positions vulnerable to this sort of treatment. Once the Japanese lost control of the sea, many garrisons found themselves on an island cut off from resupply or retreat, without much in the way of technology beyond rifles, mortars and machine guns with a little bit of ammunition. When a huge invasion force arrived, bringing naval guns, rocket-firing barges, massive airpower, flamethrowers, tanks, and other accoutrements of war, it would begin pounding the Japanese positions relentlessly. There might have been little opportunity for the Japanese to offer to talk or make any communication at all.
Attacking a person parachuting from an aircraft in distress is, in fact, prohibited by international humanitarian law (the body of international law that governs what is and what is not allowed in armed conflict). A breach of this provision would be a war crime.
The website of the International Committee of the Red Cross (which is the body tasked with monitoring the compliance with international humanitarian law; it is an NGO but a special one, being recognised as a non-state subject of international law) has a page on it. They refer to a 1977 protocol as well as a 1923 codification called the Hague Rules of Air Warfare, as well as the military manuals of many countries, and they seem to regard it also as part of customary international law (and thus also applicable in the absence of a treaty). the prohibition covers, however, only people parachuting in distress, not paratroopers descending in preparation for an attack.
During the Falklands War, there were exchanges of fire between low-flying ground-attack aircraft and small-arms equipped infantrymen. British soldiers reportedly shot at Argentine pilot who had ejected and was parachuting down.