https://www.devex.com/people/can-i-upgrade-my-seat-with-an-infant-on-delta-airlines-2348064
https://www.devex.com/people/add-a-lap-baby-to-an-existing-booking-with-delta-airlines-2348109
https://www.devex.com/people/does-frontier-require-a-separate-check-in-for-infants-2348717
https://www.devex.com/people/can-i-book-an-online-flight-for-an-infant-on-frontier-airlines-2348741
https://www.devex.com/people/does-frontier-allow-last-minute-bookings-for-infants-2348807