Huh? What?
He was a refugee that France couldn’t deport back to Iran but was not allowed to enter France (to simplify a long and complicated story).
Also a good case in point that trying to travel while stateless and carrying no paperwork sucks.
No airline will be obliged to fly you home for free; it’s your responsibility to leave the country that you have entered legally but have no right to remain in once the requirements for being there expire.
What will happen in your case is that once your passport expires, your stay in that country becomes illegal, and you are under an obligation to leave it. It’s your responsibility to comply with that obligation, and you bear the costs of complying with it. If you don’t do so, and simply remain in that country, nothing will happen immediately, though from a legal point of view you are staying there illegally and in violation of your obligation to leave. If this state of affairs persists for a longer period, it’s possible that, ultimately, the authorities of that country will deport you by forcibly putting you on a plane out. Whether the airline will be obliged to haul you back even without payment depends on the law of that country; under German law it wouldn’t be the case because you were not turned away at the airport - you were allowed to enter the country upon arrival, and what happens after that is not the airline’s business anymore. So the government of the country deporting you would pay for your flight back. They will make efforts to reclaim these expenses from you, though, and these efforts may or may not be successful.
That’s a combination of the plot to the Steven Spielberg/Tom Hanks film The Terminal and the story that inspired it, that of Mehram Karimi Nasseri. As @DPRK said, his story was rather complicated; suffice to say that a major part of the blame lies with Nasseri himself, and that he could have left the airport if he had taken up offers from the authorities of the countries involved.
Also note that Nasseri wasn’t a national of the country he intended to enter, so it’s not really a counterexample to my point that your own country will not refuse to allow you back in simply on grounds of an expired passport.
Note that according to the Wiki article you linked to, the first of those offers came in 1995, and he had been in the airport since 1988.
That’s for explicit offers to admit him into one of the European countries that he was initially pushed around between. But - at least this is my understanding of that story - he could, at all times, have gone back to Iran, a country whose nationality he possessed. So it’s not as if he didn’t have a country to go to; rather, it’s that he didn’t want to go to the country he could have gone to, and the countries he wanted to go to weren’t willing to admit him until years after the start of the story. In any case, the story is not accurately summarised by saying that he was a person without a country.
If you’re a citizen, then you are allowed back in.
Your problem will be to prove that you are a citizen.
If you look around in the arrivals hall at the airport, you will usually see a room off to the side labeled “police and immigration authority” or something similar.
And it you look through the window in the door, you will some people sitting VERY nervously in front of the officer.
(and if you look carefully, you may notice that some of those people are in handcuffs. 
)
All y’all are makin’ this waay too hard.
The standard leave for a tourist to enter a country is 6 months. Said another way, even as between countries that do not require visas, any tourist entering has a de facto visa good for (usually) 6 months.
It’s simpler for the country you’re visiting to have the visa expire before the passport. Therefore the passport must be valid for more than 6 months in order for it to be valid when the visa expires. At which date they put an order in their computers for you to be picked up on sight and deported.
The airlines don’t set the rules. They just follow them. The required passport validity period does vary by destination. But since the vast majority are 6 months, that’s the example you commonly see.
The airline violating the destination country’s laws on what people airlines may bring to their borders is on the airline. As in per-person fines, plus a need to haul the sorry passenger back home.
You overstaying your tourist authorization, visa, or passport expiry is on you. Prepare to be deported at your expense.
Different violations of different laws by different actors have different consequences.
So if I try to visit (say) France with a passport that will expire in five months the French authorities will refuse me entry?
Depends. If you have a passport of another EU member state or of an EEA member state you’re good to go. But if you are carrying some other passport you are at risk of being denied entry.
And if you are denied entry, the carrier that brought you there has the responsibility for bringing you away again. Which, even if they might ultimately recover the cost from you, is a pain and a hassle and a risk they’d rather not expose themselves to. So they don’t bring you there in the first place.
(And, the airline is probably not going to make the distinct between somebody seeking to travel to France on a close-to-expiry passport of another EU member state, and someone on a close-to-expiry passport from a third country.)
Basically, “must have at least 6 months left on passport” is a handy one-size-fits-all rule that airlines can apply to avoid a large proportion of the cases that might otherwise lead to them being obliged to bump a paying passenger at short notice in order to repatriate a denied-entry passenger.
6 months is also the usual limit for staying in a country. It’s so standard, that most countries have a stamp that says “six month, no employment” in English, no matter what the language of the country is.
If you want to stay longer, you need to submit some kind of paperwork that gets you permission to stay longer, like admission to a university, which will get you a stamp that says you can stay as long as you are enrolled full-time in the school, and possibly one that permits you to be employed for work-exchange by the school, or for no more than n hours a week, where n is a specific fraction of what is considered full-time there. In that case, you have to have more time on your passport. Other eligible paperwork for an other-than-six-month stamp might be a certificate of marriage to a citizen.
Also, six months is what you need on your passport to enter a country, not to be there, nor to exit. You might enter, for example, Israel, with eight months on your passport, and indicate that you want to stay for four months. You will be allowed to enter. If for some reason the police need to examine your passport while you are there, and they notice that it expires in five months, you have not broken the law. You might get asked if you already possess a return ticket, and when it departs, and if your answer has you leaving before your passport expires, you are fine.
This makes sure that the airlines do thorough checks. If they were not liable, some wouldn’t bother.
Indeed. When you check in for a flight to a country that you need a visa for, the airline will verify if you actually have that visa. If not, they can refuse to fly you (and there is a clause to that effect in the terms of carriage).
Of course it’s still possible that you have a visa and yet are denied entry upon arrival; that’s a residual risk which always remains and cannot be eliminated by the airline. But such cases are rare, so a visa check upon check-in greatly reduces that number of cases in which the airline will have to fly the passenger back.
This generally applies if you need a visa, but in general it is a Really Good Idea to renew your passport well ahead of time so that you do not have issues like this. I don’t know about the USA, but renewing my UK passport took around three months. Bureaucracies are not known for their speed. Nor are border guards required to let you in if they think your documents do not pass muster. You can argue all you want, but it is generally a fruitless activity…
It can also rely on warm relations between two nations.
Some years ago, I (a Canadian), attempted to travel to the US. My passport was rejected by the US passport-reading machines at US preclearance at Calgary Airport, as being “less than six months.” But it should be still valid for entry into the US, right? I was directed to a US officer, who, as things ended up, just laughed.
I was going to Las Vegas for a week on vacation, had a confirmed reservation at a hotel, and had a return ticket. The US officer just laughed after learning all that, allowed me entry into the US, and wished me luck at the tables, in spite of the fact that my passport expired in four months.
I’ve had an experience of that sort once when I wanted to cross the land border from Hong Kong to Shenzhen in Mainland China (from an immigration perspective, Hong Kong operates as if it were an independent country). I had a visa for Mainland China, but my passport was very worn and about to disintegrate because it had suffered in a downpour of rain some time before. The Chinese immigration officer examined the passport very closely; I think the issue was that it looked as if I had tampered with it to remove some pages. In the end, he decided that things were fine and let me through, so it ended well. I did take it as a hint, though, to get a new passport after my return home, even though the old one was still quite a way away from expiry.
Another worry that I’ve had (incidentally, also in China, but during another trip) was that we Germans, being as vain and fond of titles as we are, put Ph.D.s into our ID document - they’re included in the family name line. So that line in my passport reads “Dr. Schnitte”, whereas the machine-readable line at the bottom simply has Schnitte. I was worried that this discrepancy might be misunderstood in countries that don’t include such things in ID documents, and lead to me being turned away. Didn’t happen, though.
I heard of similar things while I was working at a language school in London many moons ago. Arab and Iranian students often had a problem with officialdom due to the transliteration of their names.
Slightly off topic, but I heard of a case where a German policeman took down the details of an errant Polish driver and duly sent the papers for a traffic fine. Addressed to a “Mr Driving License.” As they used to say on the US forces FEN network, “a little language goes a long way.”
I could see that happen. Poland is next to Germany, and there are millions of Polish people living here, but native Germans would be very unlikely to ever learn the language (unless you have a personal reason for it, such as being married to a Polish spouse). It’s also a language which, due to its Slavik origin, sounds very unfamiliar to Germans; there aren’t many cognate words that you could easily identify.
Tell me about it. I did Russian at university, and my knowledge is very rusty now, but it only helps me so much when learning Polish, which in some cases has grammar that is more complicated than Russian. I probably sound like a Russian when I try to speak Polish, partly because the stress is often different. Mrs Ded is of course very keen on my learning the lingo, and it is well nigh essential for shopping locally - given that some of the shop assistants are Ukrainian And that’s a funny language, sort of Russian but with a Polish flavor.
My passport is good for another 18 months, but I’ll renew it well ahead of time. Never, ever piss off immigration officials.
Right – this touches back on the OP question – my passport is valid up to the expiration date for the purpose of the US State Department identifying me as a citizen, and “request[ing] all whom it may concern to permit the citizen of the United States named herein to pass without delay or hindrance and in case of need to give all lawful aid and protection.”
The country I am traveling to OTOH as a sovereign state can make its own rules as to under what terms and conditions they’ll entertain that request.
And yes, it is always a good prudent measure to renew while you have plentiful time to do so and no immediate need to use it, in case the bureaucracy grinds slowly.