VietJetAir places firm orders for Airbus jets    A worker pumps fuel into a Vietjet Air A320 aircraft, in front of a Vietnam Airlines aircraft at Tan Son Nhat airport in Vietnam's southern Ho Chi Minh city October 20, 2013. Low-cost Vietnam airline, VietJetAir, placed an order for up to 100 Airbus (AIR.PA) aircraft, the latest entrant seeking to tap into a booming Southeast Asian market. The airline placed a firm order for 63 jets and 30 purchase options and will lease the remainder, VietJetAir officials said at a signing ceremony with Airbus at the Singapore Airshow on Tuesday. The purchase agreement covers firm orders for 42 A320neo, 14 A320ceo and seven A321ceo. Last year, privately owned VietJetAir and Airbus agreed a provisional order for the 100 jets but the deal did not show up in the order book of Airbus in its 2013 data. A firm order is seen as a strong indication of future revenue for airplane manufacturers and triggers a deposit from airlines. Airlines mainly pay for aircraft when they take delivery and usually win significant discounts for large orders. Reuters