https://www.devex.com/people/does-united-have-a-24-hour-cancellation-policy-2279716
https://www.devex.com/people/faq-how-close-to-departure-can-i-cancel-a-flight-delta-2280907
https://www.devex.com/people/how-to-call-united-help-center-speak-to-a-us-real-person-2279246
https://www.devex.com/people/how-to-call-united-help-center-speak-to-a-us-real-person-2279246
https://www.devex.com/people/how-do-i-talk-to-delta-airlines-customer-support-agent-2279588