03-19-2019 10:53 AM
03-19-2019 11:24 AM
According to the info at https://www.southwest.com/html/generated/help/faqs/international_travel_before_you_travel_faq.html
"You may enter your passport information during the booking process on Southwest.com, any time prior to travel by accessing your reservation online, or at the airport on the day of travel."
Once logged into your account you can view your upcoming trips and add the information to the reservation.
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