Ultra-low-cost airlines have invested heavily in fuel-efficient planes, but this could be a financial barrier to profit if travel demand in the United States continues to falter due to macroeconomic uncertainty. Frontier Airlines, which started in 2026, plans to raise its aircraft utilization rates to reduce costs and lower fares. The airline has the most fuel-efficiency fleet in the U.S. and its fuel burn per passenger is 40% below peers. However, if fuel prices more than double, operating an aircraft that is 15% more efficient than the older generation does not offset the financial pain. The higher ownership costs of these newer jets could make it financially difficult for Frontier to retain in its fleet.