It’s that last 4 of ssn if you’re a non-cadet.
If you’re a cadet, it’s by date of cadet orientation.

It's last 4 of social (0000 is more senior than 9999), after the cadets in your class. Some classes let the more senior classmates pair up with junior classmates and other classes go strictly by seniority order. If you're really concerned, make friends with the more senior cadets and lock up a sim partner on day 1.

Awesome, thanks for the clarification guys!

Hmm. 0000 more senior than 9999?

Just for this situation the lower digit is higher or all the lower numbers are higher in seniority? Like 3567 > 5676 ?

Correct, 3567 would have seniority over 5676 based on this scenario. The lower your first 2 digits are, the higher the seniority (based on this info and scenario)

0000>0300>1000>2000>3567>5000>5676>7000>9902 Yes, the lower the number, the more seniority in the class you have. Theoretically, your last 4 could be 0200 and you could be last in the class. 6 months after IOE, I don't know that it matters anymore...

Night time Requirement
 

Does Skywest accept new hirers with 75 night hours with at least 45 night landings or does it have to be 100 night hours? Thank you.

Yes, they do, assuming the 45 night landings were to a full stop...which meets the FAR requirements.

yes. to help clarify 999-99-0001 is senior to 111-11-9999.
Yes your seniority in class matters years down the road when you and your new hire class mate are in the same seat in the same base, or bidding for the same seat in the same base. but there is not a thing you can do to change your seniority in class since your SSN was most likely assigned well before you ever started any flight training, and if you don't have a SSN when you get hired then good luck requesting a Low last 4 on whatever government document they use to determine your seniority. Don't worry about it, it is what it is. You'll find out your seniority when you see your name plate somewhere in the room in new hire training and the only thing you can do to improve your seniority is get a cadet date ASAP, be a ramper or gate agent or cross utilized agent, or even a flight attendant ,while you're waiting to start class, or to start class earlier.

Thanks for the clarification andgood to know. I was kinda bummed thinking my social is low on the seniority as the last 4 digits start with a 2, but this info feels refreshing especially with my class date approaching next month.