I take my Southwest Airlines check-in rituals very seriously. Southwest is one of the few airlines that does not assign seating or a boarding group in advance. (unless you pay for early bird @ $15)
Exactly 24 hours before your flight is scheduled to depart you can check-in to your flight and lock-in your boarding position. That position, assuming you didn’t book a business select fare, will be somewhere between A16 through C55.
If you are on the largest plane in the Southwest fleet, their 737-800 that seats 175 pax, the last person on a full flight would be C55. On their smallest 737-300, last person to step onto a full flight with 137 pax would be C17.
Seating on Southwest works in a first-come first-serve basis, AKA “open seating”. That means the only thing you can control is your boarding position by checking in EXACTLY at the 24 hour mark. If your flight is set to leave the following day at 5:00PM, you should be ready to check-in at 4:59PM, 24 hours in advance.
First things first, you can pay $15 per person per direction (one-way), for early bird check-in. You must purchase this more than 24 hours before your departure. If you are cheap like me, you won’t drop $15 to secure your boarding position. (Plus it is so much fun to rapidly click the check-in button at the 24 hour mark like you are playing a game of Asteroids.)
Here is what NOT to do. If you are checking in multiple people at the same time, make sure to use separate browsing sessions. If you, your spouse, and a kiddo are flying on the same flight, you will EACH have to check-in for your flight at the 24 hour mark.
A few weeks ago on our quarterly trip back to Sacramento, I attempted to check Alyssa and I into our flight using two Chrome browsing windows, bad idea. As someone who works for a web-based company, please don’t hold this mistake against me. (that 24 hour excitement clearly didn’t have me thinking straight)
Without realizing, I checked myself in scoring an A60 spot in line, however Alyssa was never checked in. Southwest refreshed both check-in pages with my details because I clicked the “check-in” button on my window first. It took about two minutes to realize what had happened, by then the damage was done. Alyssa was slapped with a B28 boarding position. (fortunately, we were able to sit by one another)
I felt bad because I immediately (two minutes later), realized why the webpage had wigged out. Some secure websites don’t like two instances open at once.
Moral of the story, make sure you are using separate browsers for each passenger if doing bulk check-in; IE: one person in Chrome and the other in Firefox. Another option would be to open a second incognito window which starts a NEW private browsing session. Never again.