60da59b1_Frontier_Travel_Policies__Documentation_required___
[Type of Emergency Event...] Illness of the customer, a travel companion, or an immediate family member [Options available to you...] Change your travel date, time, and/or destination for up to 90 days from the original date of purchase with no change fee (any fare difference will apply) [Documentation required...] 
A doctor's note in writing stating that you are unable to fly on the original travel date. The certification must be signed and dated on the physician's or hospital's letterhead. The note should state the relationship to the ticket holder if applicable.
Frontier Travel Policies
Documentation required...