Raytheon [RTN] said it is developing a variant of its air-to-air missile system known as AMRAAM that will operate from the ground with extended range with a capability of reaching higher altitudes.Raytheon is calling the system AMRAAM-ER and said the new system will be faster and more maneuverable than its airborne system and will leverage the existing capabilities in AMRAAM."With AMRAAM-ER, Raytheon is rewriting the book on ground-based air defense,” said Mike Jarrett, the company’s vice president of air warfare…