Emirates invested over $15 million each to refurbish its 777-200LR in a new two-class configuration in 55 days initially then 35 days. In the mid 2000s, Formation Design Group proposed using the taller wide-body cabins to layer the bed and seat arrangements for higher density. Revealed at Aircraft Interiors Expo 2012, Factorydesign devised a double-deck system of pods for 30% more density, between premium economy and business class. In 2015, Airbus filed a patent for a double-deck business class cabin, to monetize the vertical space. Cabin pressurization is the active pumping of compressed air into the cabin of an aircraft in order to ensure the safety and comfort of the occupants. It becomes necessary whenever the aircraft reaches a certain altitude, since the natural atmospheric pressure would be too low to supply sufficient oxygen to the passengers. Without pressurization, one could suffer from altitude sickness including hypoxia. If a pressurized aircraft suffers a pressurization failure above 10,000 feet (~3,000 meters), then it could be deemed as an emergency. Should this situation occur, the aircraft should begin an emergency descent and oxygen masks should be activated for all occupants. In the majority of passenger aircraft, the passengers' oxygen masks are activated automatically if the cabin pressure falls below the atmospheric pressure equivalent of 14,000 feet (~4,500 meters). The first class section of an airplane is the class with the best service, and it is typically the highest priced. The services offered are superior to those in business class, and they are available on only a small number of long flights. First class is characterized by having a larger amount of space between seats (including those that can be converted into beds), a personal TV set, high quality food and drink, personalized service, privacy, and providing travelers with complimentary items (ex. pajamas, shoes and toiletries). Passengers in this class have a separate check-in, access to the airline's first-class lounge, preferred boarding, or private transportation between the terminal and the plane. Due to its high cost, there are few airlines that offer this service. Business class is more expensive, but it also offers more amenities to travelers than the classes below it. These may include better food, wider entertainment options, more comfortable seats with more room to recline and more legroom, among others. "Premium" Economy class is a travel class offered by some airlines in order to provide a better flying experience to the economy traveler, but for much less money than business class.