I don't normally take sides in these arguments, but I think you're misunderstanding the economics of this situation. This isn't analogous to file sharing, because file sharing doesn't affect the availability of the original file. Consider these numbers (made up, but probably not wildly inaccurate):
- Access costs $10
- Total bandwidth available is 5Mbps
- 10 users purchase access for an average of .5Mbps per user
If 10 more users pay for service, the original 10 are getting half of what they used to for the same price. In response to this (see other comments about "gouging"), airlines raise the prices of access. This act preserves some minimum level of service for those who are willing to pay.
If, instead of the scenario above, the second 10 users go on to use the service without paying, the first are "cheated" out of being able to get their minimum acceptable level of service even if they would choose to pay a higher price. When this happens, prices can be set arbitrarily high without having the intended effect of reducing the strain on the network.
Based on this logic, I disagree with your analogy to file sharing, but I also agree with you that this is not theft. It's more akin to pollution than anything else. If one chooses to smoke in a bar that doesn't allow smoking, everyone else suffers. In the same vein, if I access this service without paying, all of the paying users really do get less than they're purchasing.
The airlines are left with two choices here:
1) Plug the hole so this is no longer possible. This is the path they'll choose because it's profitable and it satisfies the already-paying users.
2) Open it up for everyone. This is impractical. If you've ever used Wi-Fi on a Bolt or Mega bus, you know that it can be painfully slow. There's no incentive for the provider to upgrade, because they can't profit by doing so.
This isn't really about taking from the big, bad corporations. It's about taking from your neighbor. It would be great if we had in-air broadband, but until that day, we'll have to find some way to regulate the use of a limited resource to prevent it from becoming over-saturated.
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Edit: formatting, clarity.