As of this writing (May 2003), the airplane leaves Ensenada's military air field every Wednesday. The company, Aero Cedros, can be reached by the following telephone number: 011-52-646-177-4503.
I have not been able to find any information on the internet about this service. When I spoke with their representative, she told me the fare was approximately 2300 pesos round trip (about $230 US). The two-propellor plane used is a Convair 440. When I was on it, it surely seemed to have seen service during WW II.
It is a thoroughly enjoyable plane flight-no flight attendants serving cocktails, no televisions, no distractions. Just the circular humming of the propellors! Some of the seats have been removed for extra cargo storage space. The families on Isla Cedros use the airplane to bring supplies and other needed items; the stores on the island are small, family-run operations. Certainly larger household items are brought in by boat, but that is not as fast. Many of the families (most work for the cooperatives on the island-either fishing, diving, or salt-processing) also have homes in Ensenada.
There are rumors of daily service from Guerrero Negro to Isla Cedros; although I have also flown this route, I cannot confirm the frequency nor cost. Apparently, it is run by a different company.