I just looked at that contract of carriage. Force majeure? They can't just say Act of God like everyone else? So if the delay is due to weather or ATC, Frontier has no obligation beyond offering a refund, is how I read it. If they want to be nice they will offer a seat on next available. I wouldn't count on Frontier helping if worse comes to worse, plan on getting home with my back-up plan, and fight it out with them afterwards to be compensated, and not with those worthless vouchers.