Electric aircraft (EA) reliance on volatile electricity prices introduces significant financial risk, a challenge often overlooked in strategic planning. We develop a profit maximizing Mixed Integer Linear Program (MILP) with a novel circular-route design to optimize strategic electric airline planning problems, including charge decisions and mixed fleet composition. Our results show that ignoring electricity prices can lead to >35% profit losses during volatile periods. While average prices mitigate this, accurate prices perform best, enabling charging arbitrage such as ferrying and skipping that boosts profits by 1.1% over simple heuristics. A mixed fleet of both electric and kerosene aircraft offers additional benefits, unlocking synergistic profit gains of up to 1.5% while maintaining the financial stability of a pure kerosene fleet. In such a fleet, kerosene aircraft form a network backbone, seen by a 10% kerosene fleet share covering almost 80% of routes. The path to sustainable aviation must therefore anticipate monthly network changes to remain optimal, incorporate accurate electricity prices for strategic charging optimization, and leverage mixed fleets to ease the transition to a more electrified future.