score:4
Normally, airlines donβt care about further first names or βmiddle initialsβ; you can simply use a single first name for booking (and have a matching passport or ID).
There are probably some minor exceptions, especially when you travel in the US, and want to use TSA Pre or CLEAR - they expect a full match with all first names. You could still travel, you just might not get TSA Pre.
This is different for Visa (and Visa Waivers, etc, like ESTA) - usually the names must match completely and fully.