Frontier Airlines has launched eight new routes on city pairs previously served by Spirit Airlines, moving quickly into markets the Florida-based ultra-low-cost carrier has abandoned.

The route additions mark the most visible network consequence to date of the consolidation between the two largest US ultra-low-cost carriers. Frontier completed its acquisition of Spirit earlier this year, and the integration has already begun reshaping route maps at both airlines.

Spirit spent 2024 and early 2025 cutting unprofitable flying as it worked through Chapter 11 restructuring and then merger integration. Those exits left city pairs without nonstop budget-carrier service — capacity Frontier now intends to capture with its own aircraft and cost structure.

The eight routes represent a transfer of market positions rather than net new capacity across the industry. For Frontier, the move extends a strategy of targeting leisure and visiting-friends-and-relatives traffic on thin routes where the Airbus A320neo-family economics allow the airline to price below legacy competitors.

For passengers, the practical effect is continuity: markets that lost Spirit service regain an ultra-low-cost option, with Frontier's bundled pricing model — including its premium seating options — replacing Spirit's à la carte structure.

The route transfers also signal how quickly Frontier intends to act on merger synergies. Network realignment, rather than fleet integration, is typically the fastest source of value in airline mergers, and Frontier is pursuing that value while the slower work of combining fleets, certificates and crews proceeds.

Frontier has not specified whether additional former Spirit routes will follow, but the carrier has signaled that further network adjustments remain under review as integration continues.