In the aviation industry, a "ghost flight" refers to a commercial flight that is operated with an aircraft containing zero or very few passengers (often defined as less than 10% capacity). These flights became a major topic of controversy during the early 2020s. The primary reason airlines operate them is to preserve their "use-it-or-lose-it" airport slots. At major hubs like London Heathrow or JFK, airlines must use their allocated take-off and landing slots at least 80% of the time; if they fail to do so, they risk losing the valuable slot to a competitor in the next season. Consequently, even if there is no demand, airlines may fly empty planes just to maintain their legal right to the route. Critics and environmental groups point to ghost flights as a major source of unnecessary carbon emissions and waste. While regulators implemented "slot relief" during the pandemic, the return to strict rules in 2025 and 2026 has reignited the debate over the environmental ethics of flying empty "specters" through our skies just to satisfy administrative quotas.