global.AIRCRAFT_UPGRADES = [
    "lv_aircraft_engine",
    "hv_aircraft_engine",
    "ev_aircraft_engine",

    "black_steel_plated_airplane_propeller",
    "redblu_steel_plated_airplane_propeller",
    "stainless_steel_plated_airplane_propeller",
    "titanium_plated_airplane_propeller",

    "redblu_steel_landing_gear",
    "aluminium_landing_gear",
    "stainless_steel_landing_gear",
    "titanium_landing_gear",

    "redblu_steel_hull_reinforcement",
    "aluminium_hull_reinforcement",
    "stainless_steel_hull_reinforcement",
    "titanium_hull_reinforcement"
]

global.UNIVERSAL_CIRCUIT_TIERS = ["ulv", "lv", "mv", "hv", "ev", "iv", "luv", "zpm", "uv", "uhv"];