[brainless]

Airlines have alliances, it does not stop you from taking any airline you want for your route, but costs may vary.

It is just a property of networks. As an end user you still get to use all providers, but two of them may use a dedicated connection to reduce internal prices (the price benefit of which they may or may not give back to the user).

Neutrality from the point of the user is not affected when it comes to service being available.

Now if one airline alliance said you are not allowed to get on their flight if you hoped off from a rival alliance, then we have an issue.