https://central.xero.com/s/question/0D58V00009hMfR7SAK/understanding-deltas-rulesdoes-delta-have-a-cancellation-policy-travelhack
https://central.xero.com/s/question/0D58V00009hMfR7SAK/understanding-deltas-rulesdoes-delta-have-a-cancellation-policy-travelhack