Metal
noun
1. Frequent flyer speak for "plane", Metal refers to the actual owner/lessee of the aircraft, regardless of the ticketing airline. For example, a British Airways ticket might be ticketed as British Airways but all or part of the itinerary might be on American Airlines metal (American Airlines planes...). This is important because mileage earnings and upgrade redemptions are often restricted to the home airline's metal (e.g., you can't use United miles to upgrade on Lufthansa metal).
