I think you will see consolidation within the ULCCs. The pricing and business model of high-utilization ULCCs is proven in Europe (Ryan Air, Easy Jet, Wizz, etc.) and is a power. The LCC model is dominant in the US because its basically WN and then some others. WN is getting bloated and their prices are rarely the lowest, so I do think that there is still a demand for ULCC in the US but I doubt it will ever get to the market size of Ryan Air and Easy Jet because Southwest already assumed that vacuum.

Marg is certainly correct that Allegiant is having a hard time growing because of labor (pilot and flight attendant) shortages. Flight attendants are not paid any where near a career type wage and pilots are grossly underpaid. The QOL is awesome for some, but can be dreadful for others. The disparity in QOL at allegiant is immense because of our small bases and unusual Florida base setup.

Just my two cents...