Working for a travel agent, you learn a few tricks.
Bring the airline’s own Rule 240 policy with you to the airport. You can find this as a PDF file on any airline’s website as their “Contract of Carriage”
Frontier’s is here: http://www.frontierairlines.com/frontier/pdf/Contract_of_Carriage.pdf
Rule 240 is on page 58. Print that page!
For example: Delta
http://images.delta.com.edgesuite.net/delta/pdfs/contract_of_carriage_dom.pdf
Delta’s rule 240 is on page 47.
Rule 240 basically says that if the delay or cancellation was caused by the airline’s fault (equipment problems, scheduling problems, crew problems) then they must fly you on another airline to your destination.
This does not apply in the case of weather-related delays.