Boeing 747-400 Jumbo jets, which defined a carrier's status and a whole era in aviation, are rapidly declining in popularity. Korean Air plans to sell 15 of its fleet of B747-400s by 2017, and Singapore Airlines already halted international flights using the B747-400 last year. Other carriers around the world are following suit. The jumbo, which began commercial flights in 1988, is 70 m long and 19.33 m tall and can carry 400 passengers for more than 16 hours. Attesting to its level of comfort, Cheong Wa Dae even leased a B747-400 aircraft as the official presidential plane in 2010....