You can. I would highly suggest once you make a decision to call and resign your place in class. Thank them for the opportunity but let them know a better offer came up. Last thing you want to do is no show day 1.

The way things are looking you should

1) take the very first date possible
2) shoot for stability over all else (dunno exactly what that means but take your best guess)

Be very cautious about this. Give them a notice you see as sufficient, but understand that classes can be canceled. If you have declined an offer, then a week prior to class your first choice cancels your class I can guarantee that the other offer won't stand anymore.

Saw one guy get burned doing this when multiple companies he had accepted offers from tried to book him with the same 3rd party CTP vendor.

You’re not hired until your butt is sitting in class. If you get caught playing games, as defined by the airline, you’ll be out of luck. Pick one and thank the other two for considering you. If something then happens to the offer you took, you’ll be in a much better position to call your second choice and get a class date.

Don't go to skywest.

They don't like redheads?

Better go to Expressjet, right?

Right. They've never furloughed a pilot. Definitely don't want to miss your golden opportunity for furlough bragging rights, especially with coronavirus looming.

You're not a real pilot until you've been furloughed, gone out on strike, and been divorced. Be really cool to check off one of those boxes just weeks into your career. If you're lucky that might lead to another box checked in short order, if your wife expects you to have an income.

The downside of Skywest is you won't get to check the strike box.

On a serious note... if you're looking at any small botique regionals, better do your homework. Those seem to be subject to being spontaneously liquidated even in the best of times. Make sure you understand their financial, operational, and contract status.