Frontier is racing to become a duplicate of Spirit Airlines...
I don't know if you're checking luggage but they charge and just raised their fee on it while Southwest still provides the first two checked bags free, up to 50 lbs. each.
http://www.usatoday.com/story/todayi...fees/25093975/
Not that Southwest is perfect but Frontier has become complaint central as of late.
http://denver.cbslocal.com/2015/03/2...-compensation/
http://www.bizjournals.com/denver/mo...amid-tech.html