Not airplanes - area codes. State regulators want to create a 747 area code for the southwestern section of the San Fernando Valley (roughly from Van Nuys to Westlake Village). They haven't decided whether to actually split up the region - again - or create an overlay for all new numbers. The overlay allows current phone customers to keep their 818 area code, but would require them to dial an area code for every call, as is now done in the 310 area. Either way, businesses and residents aren't happy about it; new area codes can be a hassle - and an expense. Say, does anyone still remember all the fuss when the Valley changed over from 213 to 818? (LAT)