Frontier airline is like Spirit or Delta
 

Frontier airline can be compared with the low budget and low service of Spirit airline or it is a
value budget like Delta airline

Getting USD45/- cheaper fare on it as compared to Delta for the sector NYC - Miami

thanks

Frontier is much more like Spirit than Delta. It's a discount, lots-of-extra-charges airline with limited planes and routes. To me, it's not worth saving $45. Add up all the extra charges to be sure, however.

Be aware that not all 3 NYC airports are the same. If you are leaving to FLA from Teaneck NJ, then you should use Newark Airport, and not LGA or JFK.

If you are leaving from Manhattan, then you could use any of the 3 airports.

Frontier was reorganized a few years ago into an ala carte airline - very low fares but charges for everything but the restrooms. No real comparison to Delta. Apple and oranges.

Delta, United and American are just regular airlines. Delta is not a "budget" airline in any particular way.

I don't think focusing on extra charges for particular things is the problem nor the way to go, they must be disclosed and should be notated when booking. Sure, you may have to add a few things up to get the total price, but it must be included in the total price before you hit the final booking click.

What I would worry about are the complaints, service, quality of planes, etc. And Frontier has a bad complaint record, NB
http://www.denverpost.com/business/c...eft-hold-hours

Better airlines are Delta, United , American and JetBlue ... Right?

Yes.

And is American airline the best in domestic American Airlines?

No, American is not the best rather one of several regular airlines like United and Delta.
Southwest is an excellent airline with more budget friendly prices if you buy far enough in advance. Free baggage and no change fees.