You presumably know this but just to clarify for other readers: it's if you willingly give your data to a third party (the airlines) and the third party willingly gives it to the government, then it's not a violation for the government to use it.

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.

"Willingly" needs an update in the age of hidden and unreadable ToS agreements and data brokers. I willingly board a plane, which the airline takes to mean that I willingly agree to their contract of carriage, so I willingly hand over my data to a data broker that passes it to the government. But was I really agreeing to any of that?

Which is an insane doctrine in 2025 although I can see how it made more sense historically.

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.