Your assertion that "Phone companies lock people into contracts" is not true for everyone. Some phone companies lock some people into contracts is true. But, again, it is not true of everyone. While consumers may not have all the choices they deserve, they do have some choice.
Look at it this way: If Comcast wants to expand its Xfinity subscriber base in a particular area, and a lot of Internet users in that area are already locked into contracts with the phone company and the satellite TV company, it'll have a hard time selling Xfinity subscriptions unless it can afford to buy out the ETFs of the competitor's subscribers. Now replace "Comcast" brands with ViaSat, its competitor with Gogo, and "Internet users" with airlines.
If any competitor wants to expand into an area where another competitor already has contracts, yes business will be difficult initially, but what again is your point? This is how businesses has been done forever. In your example, Xfinity can entice potential customers to switch when their contracts run out. They can blanket neighborhoods with flyers about cheaper rates. Or Xfinity can offer to pay for any early termination fees to win customers.
In the case of airlines, Gogo was the only option at one point. Some airlines signed contracts with them. But the airlines didn't sign permanent, irrevocable contracts. They may have signed long term contracts. But my point again is not ALL of them did. Some of them are now installing wifi and have options.
If a better competitor comes along, the airlines may not renew their contracts with Gogo. Our they could buy out of their contracts if the contract has such a clause. I would think the airlines' lawyers would have been diligent enough to put in buyout and termination clauses before entering into a long term contract.
The main obstacle here is that the infrastructure will cost billions to anyone entering into this market. That is what is keeping everyone out and why there are only a few options.
Unless Gogo has all your potential clients tied up for a decade with exclusive contracts
This was what was in the article:
At least two companiesâ"ViaSat and Global Eagle Entertainment (GEE)â"are encroaching on its airspace, winning business by offering faster, cheaper connections that use satellites instead of cell towers.
Now you are writing:
An airline that has already deployed a particular provider's service is a "client", not a "potential client". This means a "potential client" for ViaSat is an airline that 1. isn't already a ViaSat client and 2. isn't already in an exclusive contract with Gogo.
If Gogo's competitors already have contracts with some airlines, your "all" point is nonsense. That's like saying Comcast could potentially look all my neighbors into contracts. Except that it is a fact that they haven't and can't.
Of course you can't flap your arms and fly to the moon. After a while you'd run out of air to push against.