I think a closer analogue is Southwest Airlines.
JetBlue actually operate two distinct families of aircraft, neither compatible to _any_ degree. The EMBRAER EMB-180 and the Airbus 320 / 321 series.
No spares compatibility and no pilot rating across those two types. Even the seats are different widths. The only common factor is that they both burn kerosene :)
JetBlue have also introduced a second cabin product, Mint, which further complicates their operations.
Also, JetBlue already has two cabin products - the "Even More" seats, which you can book for an extra price, and give you additional legroom comparable to an exit seat, along with boarding first and a special security line with a smaller wait. On the A320 I flew a few weeks ago, the exit rows as well as the first 5 rows in the cabin were premium seats. So now you add in Mint and you basically have three classes of seats on JetBlue
I dig the model silvercar is trying to pulloff though. It is the jetblue of car rentals. Entire fleet is the same, lowers cost of maintenance (fewer spare parts, fewer training courses for mechanics, etc). They offer a premium reliable product at a fair price.
Now if only they would hook up with founderscard and setup a deal for its members...