United Airlines and the Zero Aggression Principle

United Airlines and the Zero Aggression Principle

How libertarians (should) view the United Airlines de-planing.
By Jim Babka

NOTE: This article was updated on 9/23/21

Dr. David Dao had a valid ticket for United Express Flight 3411 on April 9, 2017. The flight was full, but United Airlines needed four seats to transport its own employees. It offered vouchers to buy the needed seats, but all the passengers declined. United then selected four passengers for mandatory removal. Dr. Dao was one of those passengers. Three of the passengers cooperated, but Dr. Dao did not, because he had patients he needed to see the next day. He felt the health of his patients outweighed United’s need to transport its employees. So United had airport police use violence to remove Dr. Dao. He was knocked unconscious and injured his arm during the incident.

Was this a defensive use of force by United, or an immoral act of aggression against Dr. Dao?

United owned the plane. It was their property. But Dr. Dao had a valid contract, in the form of a ticket, to use a seat on that flight. Who committed the act of aggression in this case?

The Zero Aggression Principle (the ZAP) says that it’s wrong to use threats, backed by actual violence to achieve personal or social goals. As libertarians, we usually apply this principle to The State. But many of us suddenly lose perspective when it gets applied in the voluntary sector. There are two reasons for this…

First, libertarians haven’t really nailed down what aggression means.

Second, much of the libertarian universe has been under the thrall of an incredibly prolific writer by the name of Murray Rothbard. He taught that the ZAP is based on property rights. But it’s more than that, actually.


Libertarians usually define aggression as “initiated force.” It’s the first punch thrown or a violent act without provocation. But if you spend years contemplating this libertarian rule, as I have, you’ll come to realize that this definition is insufficient.

Libertarians are very rarely pacifists. They don’t believe self-defense or due process are aggression. And most libertarians believe in governance and value order. If you don’t believe me, go watch a bylaws debate at a Libertarian Party convention.

It’s better to say that aggression is excessive force.

One can throw the first punch to remove someone from your property, but that’s excessive force if you didn’t first ask them to leave peacefully. It’s also excessive force if you shoot them for failing to comply immediately. The amount of defensive force you employ must be proportional to the situation, otherwise it ceases to be defensive, and becomes aggressive.

Did United Airlines use defensive force or excessive (aggressive) force against Dr. Dao?

Property Rights

Numerous libertarians, discussing this matter in social media, have observed that…

  • The plane is airline property. They can kick off whoever they wish.
  • The ticket came with a carriage contract. It warns you that you may be bumped.

If the ZAP is based only on who has property rights, then United was within its rights to remove Dr. Dao, or any other passenger. But the ZAP extends further than property rights.

Natural Rights and Empathy

The ZAP is based on natural rights. And natural rights come from empathy.

The public outrage directed at United stems from the fact most people empathized with Dao. They easily imagined being in his seat. They were the traveler, eager to reach their destination. These days, flying isn’t fun. The airport is already a police state. People understood Dao’s reluctance and resistance. Being bumped is a costly inconvenience. The public was appalled — and Dao’s fellow passengers were shocked — by the use of force.

Most people hate injustice, and that’s what they saw in the viral video of Dr. Dao’s removal. The public thinks Dr. Dao was within his rights and the airline was not. The decision as to who had what right was empathetically determined by bystanders. No one would want to be treated the way Dr. Dao was.

What a libertarian would expect from United Airlines

The ZAP describes a moral duty. We cannot aggress against others. This moral duty includes a prohibition against using excessive force to defend a property right.

Politics ignores this moral duty. Instead, people delegate aggression to their most elite neighbors (politicians and bureaucrats). These elites write rules and enact prohibitions, levy taxes, and use those funds to hire and arm rule enforcers. It’s a violent system. And it shouldn’t be lost on you that United called federal aviation officers to do their dirty work.

But if the ZAP is your moral principle, then you’ll try to think of the most peaceful method to address the matter at hand. Instead of escalating violence, you’ll de-escalate it. This is what we should actually expect from all law enforcement officers. But we should have expected it all the more in this case where we had, essentially, a market-based solution that was so readily available an Economics 101 student could’ve devised it.

United should have held an auction to see who would give up their seat for the lowest price

United spokesman, Charlie Hobart, said Dr. Dao was a “volunteer.” He was, after all, offered some money to de-plane. But Dao had actually been drafted. And he didn’t think the modest money offered was worth giving up his seat.

Until the 1990s, the IRS was fond of insisting that the income tax was “voluntary.” After all, you took time out of your schedule, filled out complex forms, signed the affidavit at the end, and yielded up money. No one came to your house and put a gun to your head, right?

Some definition of voluntary! Yet it seems United bought into this definition. Perhaps that’s because The State is omnipresent in the airline industry. The law permitted United to call government enforcers to help Dr. Dao volunteer!

Let’s be clear, another seat was needed. Someone was going to have to get off the plane. But if United operated by the ZAP, they would’ve continued to seek readily available peaceful means to achieve their goal instead of giving up and calling for violence.

It’s a simple fact – an auction to find a passenger who was willing to deplane was going to find a taker. They were probably only a few hundred dollars away. Think of the money and hassle United would’ve saved themselves if they had used a peaceful auction instead of violent police action. Instead, they used excessive force to defend their property right, and thereby committed an act of aggression against an innocent person.

What libertarians expect of their Democrat and Republican neighbors

One more very sharp point needs to be made about this. Non-libertarians reading this are hypocrites. United’s decision to call enforcers to, as they put it, “re-accommodate” passengers, is precisely what your politicians do every day. Despite your outrage at United, you urge these incumbents to write new laws and collect greater levies to send enforcers to interfere in a virtually unlimited number of activities that could be solved non-violently with just a little creativity and some social acumen.

Whenever someone objects to a Democratic or Republican dictate, the enforcers don’t take it very well. They escalate rather than de-escalate the situation. The result is that people get injured and even murdered. And when that happens, most Democrats and Republicans go on to suggest that the victim had it coming, unless, perhaps, it was a member of their own political tribe, in which case the response is outrage and finger-pointing at the other political tribe!

Is violence sometimes necessary for self-defense? Might we even have to call for an arrest in some situations? Yes and yes. But aggression is a blunt, overused tool to solve problems. Excessive force as a means to solve a personal goal is immoral and should be abandoned.

There is an alternative. Free markets do a much better job of providing regulation and necessary accountability. Consider that United Airlines stock lost $750 million in a single day over this episode. No grandstanding Senator was required.

The libertarian wistfully wishes that politicians had to pay a similarly steep price for their much more frequent and very similar failings.

9/23/21 note

Please observe the similarities between the United deplaning of Dr. Dao, and the current de-platforming of various groups and opinions by major tech firms like Facebook, Google, and Amazon. Just because you have a property right to de-plane or de-platform someone doesn’t mean that you should.

United Airlines had non-violent options, and so do the big tech firms. Social media customers already have tools they can use to filter content they dislike. The big tech companies could simply expand those tools instead of censoring and de-platforming people.

There’s more to obeying the Zero Aggression Principle than simply defending property rights. Empathy, and the other natural rights that derive from it, are also important. One should never use excessive force when defending a right. The force used must always be proportional to the threat. Better yet, find a solution that doesn’t use force at all.
Jim Babka is the co-creator of the Zero Aggression Project and the President of Downsize DC.

Show Comments 11


  1. The aggression of the liar’s tongue, often precedes the aggression of the thug’s cudgel. In this United case, the aggression began with a lie, uttered to every passenger aboard the airplane. That lie, was that United owned a big-enough airplane to carry them all.

    The truth underlying this lie, is that United tricks customers into believing that the price of an airline flight is cheaper than it really is. The specific fraudulent and deceptive lie they tell customers to achieve this, is given a name in federal regulations. This lie is called “overbooking”.

    The lobbyists whom United hires, to persuade the government to ignore these lies, actually got regulations written, that make it confusing for most people to recognize that United is lying to customers to trick us out of money.

    So here’s my attempt to simplify the lie and make it understandable.

    Some passengers get hung up in traffic and miss a United flight. So United discovered it could lie to customers and pretend that it had more seats available on each airplane, than were actually bolted to the floor. (Remember…United knows how many seats are bolted to the floor of each airplane they own. There’s no guesswork involved.). Some customers get hung up in traffic and arrive late. But because United lied to all the customers, there were enough seats for the customers who arrived early but not enough to seat every customer to whom United sold a seat.

    Usually when the customers who arrive late, reach the airport, they are offered an empty seat on another flight, leaving much later that day. This enables United to fill seats on later flights that otherwise would go empty. The lying is unfair to those customers who get put on the later flight, because had they been told the truth, they would first have asked a competing airline company if a seat on the competitor’s plane could get them through, sooner. A regulation that legalizes this form of lying to trick customers out of money, already is bad, because if harms the customers both by costing them money and costing them wasted travel time.

    But what happens when the traffic is smooth and all of the customers show up on time for their scheduled flight?

    Since United lied to all the customers, pretending there would be enough seats for them all, they all are now in competition for the seats they already paid for.

    This is a property right of the customers. Had they not been lied to, they would have known​ to book a flight on an honest airline company that does not lie to them. For example, if I pay Southwest Airlines for a seat and I arrive late, Southwest keeps the money unless a standby passenger bought my seat when I failed to appear at the airport on time. I have to pay more money for a seat on another flight, if the empty seat I bought, does not have me in it. This honest approach harms me, if I arrive late. But it does not harm every passenger aboard the plane, when all of us arrive at the airport on time.

    So, the “overbooking” regulations that United lobbyists bought in Washington, empower United to use violence against customers, when United has lied to them and has gotten caught doing it.

    It’s worth considering a related question.

    How safe are airline companies who lie to customers?

    Several years ago, the Boeing Company’s 737 airliners were found to develop cracks in the metal, just ahead of the tail fin. In two of the planes, the metal broke and things got sucked out of the planes, in flight. Boeing began a safety recall, and an inspection program to find planes with cracks and get them repaired first.

    Southwest realized that the repair, a diamond-shaped brace welded to metal, made a good place to put a satellite antenna on the plane, and started offering WiFi service with the antennas. In the course of doing that, Southwest discovered that they had not been following the agreed procedure for inspection of the planes to check for cracks. They reported the problem and were fined a billion dollars. The FAA then checked, and learned that many of Southwest Airlines’ competitors were also getting the inspection done wrong. Lawyers and lobbyists fought about it instead of fixing the problem.

    That’s a clear example of why it’s safer to fly with a company who tell the truth.

    1. I agree with your point, but until ‘government’ stops it’s part in making the ‘friendly skies’ unfriendly, I won’t be flying any time soon. I would prefer to be asked questions, as the Israeli government does, to being given a ‘choice’ between a pat-down or an invasive body scan.

  2. The plain fact here is that the airline had no right to enlist the authorities to validate their civil claim. Dr. Dao was committing no crime, he had a valid ticket, and was not interfering with the operation of the aircraft, so government authorities had absolutely NO authority to enlist the aid of governmental authorities to remove him from the plane. Had I (a retired cop) been on that plane I would have flashed my badge, with the proviso that I am retired, and informed passengers that the police had NO authority to remove Dr. Dao by force. I believe that in that case passengers would have made it impossible for the authorities to act illegally as they did. The key issue here is that this was a civil matter. The authorities had absolutely no right to interfere.

  3. The sheer force of power by the state was apt to be abused when call came from a private entity with a viable market place. The airline should have handled this privately, no laws were in jeopardy if being broken. Private company’s policies might have been broken and those should be handled privately.
    The most concerning is: the initiative from the airline to call LEOs, to clean up their mess. Followed by the people’s incomprehension of government’s abuse of power. It is slowly becoming normal. Keep moving !!

  4. David, we Libertarians are fond of saying that government should enforce contracts made between private entities (rather than making laws). That’s exactly what happened here. Read your “Contract of Carriage” that actually governs the contract made between you and the airline when you “buy a ticket”. Under that contract, United was perfectly within its rights to ask the government to enforce United’s right to bump Mr Dao off the plane. (No, I don’t like it, and I think they should have auctioned the seats instead, but. . .)
    This is an example of asymmetric negotiations. Try to negotiate with United (or any other airline) to modify that Contract of Carriage. I’ll wait. You have essentially NO power to change that contract, except by talking to your congress-critter. (And you’d better have deeper pockets than I do, if you expect to see success.)
    Note that auctioning the seats may increase the average amount the airline has to pay, which will tip the scale more in the direction of risking a vacant seat occasionally. More capacity margin in the system is a good thing, as currently the airlines are trying to run 100% full planes 100% of the time. That guarantees this sort of behavior. To understand why near-zero capacity margin guarantees this, read “Managing the Design Factory” or any book about factory scheduling.

    1. Post

      The issue, actually, is the one outlined in the article itself. Libertarianism embraces contracts, of course. But that’s not it’s central idea. The Zero Aggression Principle is. There’s an imbalance in the terms of contract, in this instance — a result of a statist policy (hardly a surprise). This was not a market method or outcome. Markets seek and try peaceful options. These options don’t increase violence, instead they de-escalate wherever possible — and it was still VERY possible in this case. Contracts don’t excuse horrible behavior. The community response was swift and deserved.

  5. Governments are not here to enforce contracts they were created to protect rights. They actually just defend themselves at the cost of all governed.

    We have the right to contract. I don’t see how that translates into we have the right to have our contract enforced. Sure we have the right to seek restitution but we certainly do not have the right for immediate use of force when the contract isn’t being abided by otherwise we wouldn’t need foreclosures the bank could just have the sheriff show up, beat you, take anything of value they find to give to the bank and then lock you up in a cage because you didn’t follow your contract. The only time force should be used is when imminent use of force is being threatened or violence is being initiated.

    LEOs should have done nothing, instead they reinforced they are the largest part of the problem.

  6. The assertion that “natural rights” are based upon “empathy” is nonsense. Empathy is putting ourselves mentally and emotionally in another persons shoes. Natural rights are the result of the nature of things, or how things are in reality. It makes no significant difference how they came to be this way. In other words, no creator is required and however things came to be this way (natural), that’s the way they are.
    To assert that “zero aggression” is the primary principle is also nonsense. Aggression requires a subject and an object. These are owners of property of one sort or another beginning with self ownership. Apart from property, the idea of aggression is meaningless.
    United was apparently within it’s contractual rights to bump the gentleman from the flight and to call upon the authorities to enforce those rights. Their decision to do so was not aggression. The reason decent people were appalled at the incident is because United unnecessarily caused harm to a customer and failed miserably to do what most of us think would be the right thing to do. They should have made escalating offers to the passengers until someone was happy to give up their seat.
    If the terms of the contract which the airline requires are unacceptable to customers then they should make their preferences known and the market should address those preferences as it does in other areas. I am not familiar with the inner workings of airlines, but if government is involved in preventing the airline market from functioning properly then obviously that is a large part of the problem.

    Thanks for the work you do here.

  7. Excellent example, an auction. It is a “price discovery” method that reveals how much different individuals value something at the margin. Dr. Dao valued his seat more than many others because he had patients awaiting him. UA didn’t even try “to discover” someone who valued the seat less than Dr. Dao. Shamefully.
    Coercion or violence can be “accidental,” but this was purposive by UA, calling the airport cops to beat him up.

  8. Al United had to do was get on the PA increasing the value of their offer. No real auction is needed. Somebody would have accepted a later flight, a hotel room and more cash

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