DETROIT – (Reuters) – Virgin Atlantic [VA.UL] plans to decide within six months on how to replace seven Boeing 747s it flies from London’s Gatwick airport, and could expand its overall fleet in the process, the British airline’s chief executive said Thursday. “The options we are most serious about are the (Airbus (AIR.PA)) A350, the (Boeing (BA.N)) 787-10 and 777-300ER jets. Kreeger told a conference in November that Virgin would decide on the fleet plan within the next nine months, implying a decision by the end of August.