Purchasing from data brokers in order to avoid getting a search warrant is just unambiguously against the Fourth Amendment, right? It’s amazing to me that this hasn’t been stopped by the courts.
On the other hand, it could be argued that buying this data amounts to hiring the airline to spy on you, no different than if they had hired a private investigator to follow you. But if everything is tracked and stored indefinitely, a mere warrant isn't much of a shield [1]. Nor does this solve the problem of corporate surveillance, which I see as just as big a threat.
[1] https://web.archive.org/web/20140718122350/https://www.popeh...
Note there's an exception for cell tower data because courts ruled that cellphones are absolutely necessary for people to live their lives today. They collect so much data that applying Third Party Doctrine to that data is tantamount to a 24/7 100% carte blanche surveillance system across the entire country, so SCOTUS carved this one out.
They gotta get a search warrant for a storage locker or bank box. They ought to have to get the same warrant for your gmail or fitness app records or whatever. "Papers and effects" and all that.
Nobody is forcing these companies to do this. They just happen to have stuff the government wants to buy and are more than happy to sell it for a profit. And Congress doesn't forbid it.