There is a ton of demand to Florida right now and historically there was quite a bit of capacity across US, FL, and WN...though not as much as there is currently. This is partly why I think a F9/NK merger will see quite a bit of cuts in PHL. I do not see a combined carrier flying 6-8x to MCO/FLL+MIA, 2-4x to SJU, 2x to LAS, 2x to LAX.
On a related note, F9 has decreased PHL flights this summer but also added some. I was surprised how many markets were daily (planned for previously or now planned for) or more.
https://aeroroutes.com/eng/220511-f9jul22us?rq=frontierPHL-RDU - Increased 7x to 14x
PHL-DFW - Decreased from 7x to 4x
PHL-DEN - Decreased from 14x to 7x
PHL-FLL - Decreased from 14x to 5x (**This is a pretty big decrease)
PHL-CLT - Decreased from 10x to 7x
PHL-RSW - Decreased from 7x to 6x
PHL-MIA - Decreased from 7x to 6x
PHL-TPA - Decreased from 15 to 14x
PHL-MCO - Decreased from 33x to 32x