Even if obvious PII is removed from this data, that's not likely to add much privacy for many people - esp. employees and regular customers.
This is in part because things like patterns of email would, with fairly high probability, identify some employees in key roles - even without attempting to correlate it with external data sources.
For example using just email where pseudonyms for each person and email address replaced actual names and email addresses (both in metadata and email bodies), one could probably identify with high probably the CEO and all email communications they engaged in. Then, from that, it would likely be trivial to figure out the next layer of reports, etc.
Coupled with outside data sources, such as scraping of LinkedIn data and news sources (esp. for the highest level executives), the certainty of identification could be improved.
Or suppose a person who valued cost over service and therefore chose Spirit whenever possible has an interest in both security and very large databases and regularly attends conferences related to both. It's public information where and when each DEF CON and VLDB conference is held. Even if that person is not a panel member or presenter, one could likely dig through the Spirit traveler data and figure out that person exists and the area they live in (based on what seems to be their home base assuming Spirit flew out of there). Correlating that with comments on YouTube videos by that actual person and/or their gMail data (including "password recovery" emails and phone numbers) could reliably identify that person and their other travel could then reveal other interests (for example, it may reveal that it's likely this person is also a Furry who attends those conferences or that they may have a second spouse or lover in a particular location).
If the data is cleaned enough to prevent such exposure, it would likely be of little use to Google.
As Scott McNealy said over 25 years ago, “You have zero privacy anyway. Get over it”.