I posted this on the most recent OAG thread, but I feel it is a relevant discussion here as well.
With NK ending their PHX - DEN service in May. I have the following thoughts.
NK's strategy in PHX hasn't really made a lot of sense to me.
PHX - DEN currently sees AA, F9, UA, and WN service in addition to NK. In May here are the following frequencies / pricing on this route (as of a search tonight 2/12/17):
AA: 4x (lowest priced fares from $57 - $188 one way depending on the day of the week)
F9: 2x (lowest priced fares from $50 - $128 one way depending on the day of the week)
UA: 6x (lowest priced fares from $43 - $129 one way depending on the day of the week)
WN: 10x (lowest priced fares from $43 - $83 one way depending on the day of the week)
A 1x daily city pair on NK where 4 other carriers combined have 22x daily flights is just not going to cut it, especially when it's not a high fare route to begin with.
I don't really understand NK's strategy for PHX. Looking at NK's other routes out of PHX, they fly PHX - DFW and seasonally PHX - ORD and MSP. They also formerly flew PHX - LAX but that route was cancelled in September with multiple AA, DL, UA, and WN flights and relatively low fares.
Every single one of NK's routes (and the LAX former route) has a minimum of 2 other competitors and high frequencies. PHX - DFW has almost a dozen AA flights to DFW and multiple WN flights to DAL. PHX - ORD has almost a dozen AA flights, multiple UA flights, a F9 flight and multiple WN flights to MDW. PHX - MSP has multiple AA, DL, SY, and WN flights.
The hassle of flying NK at low frequencies for barely any savings over the competitors who offer multiple frequencies, wifi, carry on baggage at no additional charge, and much more useful frequent flyer programs just doesn't seem worth it.
F9 seems to make PHX work as they've found some unserved or underserved markets. F9 is the only carrier flying PHX - CLE, COS, and CVG. In addition, F9's other markets out of PHX are traditionally higher fare markets, markets less susceptible to competition by automobile, markets with only one other competitor, or DEN and ORD which make more sense as F9 routes due to F9's stronger presence in PHX.
Of the ULCC carriers in the PHX area. G4 has found a niche of serving secondary markets from a secondary airport (AZA). F9 has found a niche of serving markets with decent O/D numbers but are either not served or under served by other carriers out of the main airport (PHX). NK hasn't found a niche and seems to have simply decided to add flights to the markets that have the most daily non stops from PHX with the hopes that it would work. LAX didn't. DEN didn't.
To me NK has basically been throwing darts in PHX. I am a bit surprised that they are ending DEN as I believe that was one of their first markets in PHX, but it is a route with heavy competition. I am still surprised they haven't given PHX-LAS a go, seems to me that would be tailor made for them.
Additionally F9 has been a mixed bag as well. Recently they have expanded a bit more, but they've been in and out of PHX-SLC, and dropped SFO, while CLE was seasonal last year (seems that it will be retained this year). WN also flys PHX-CLE 2x during spring peak, and 1x year round. Overall my observation in PHX is that AA and WN are more than willing to match or come close to F9 and NK fares especially on shorter routes, and the value proposition to the reasonably educated shopper is undoubtedly with WN and to a slightly lessor extent AA.