What colours or markings did the aircraft have?
Do you have any pics of the aircraft? If so, there are many FReepers, such as myslef, who could help you identify the aircraft.
Sorry, I’m not a flyboy! The first few biz jets were white, too high to see any markings. They usually accompanied planes that were large and slow like old DC3’s or DC6’s. Since we moved to Big Bear Lake in 1993, I have seen several large jet-engined cargo planes flying the same route. We are at about 7,000 ft. elevation. The incoming commercial traffic into Ontario Airport, LAX, Orange County, Santa Monica, etc. all come in from the east at 15,000 ft. or more. The huge cargo planes I am talking about come from the south headed north towards the Mojave desert or Nevada at only a few thousand feet over our mountain location. All of the planes are painted like a military gray or green-gray with no markings visible to me. They are not moving super fast, but are very low and moving in a direction that no other aircraft move-either private or commercial. I have no pictures because they pass over us in about a minute. Too late to run in the house and grab a camera. When I have called the FAA in Riverside, it usually takes several minutes to grap the phone, look up the number in our phone book, dial the number and reach a duty officer. By that time , the plane has been gone by about 10-15 minutes. None of the times, has the FAA been able to tell me that they have tracked the plane.