JetBlue's new service to Boston means cheaper fares in Phila.
The times are geared more for BOS business travelers to PHL than the otherway but it makes sense given JetBlue's strength up there.
Hopefully it does well and JetBlue expands PHL w Florida service (Ft. Lauderdale-FLL and Orlando-MCO as starters, then maybe Tampa-TPA, Ft. Myers-RSW, West Palm Beach-PBI, Sarasota, FL SRQ), and more outside Florida like maybe Dallas-DFW and San Juan-SJU. I'd rather JetBlue had launched PHL-DFW than Spirit. 3 hours on a Spirit flight is torture. If American and US Airways merge, JetBlue could see additional opportunities as well.
On another note, Virgin America will begin flying to Newark as well, although Virgin is reducing PHL down to 2x daily to LAX, from 3x daily. Virgin also flies 2x daily to SFO. If Virgin doesn't perform well at PHL, I could see them dropping to just SFO, but maybe increasing it to 3x daily to SFO since SFO can handle more connections than LAX. If it ceases PHL service altogether, JetBlue could pick up the SFO service as it, unlike Southwest, isn't averse to flying transcons.