New York to San Francisco is a busy route for private jet and general aviation traffic. I would suggest that your friends begin asking around at the companies that service and support such airplanes to ask about getting a dog taken on board a flight. There are corporate and private planes flying empty all the time.
Start looking at the organizations on the bottom of the AirNav.com page for Teterboro Airport -- (http://www.airnav.com/airport/KTEB
) Because the crew on such planes won't want to deal with the dog on the ground, the owner will need to plan on taking the dog to the general aviation terminal at a New York City airport just before the plane's scheduled departure, and having someone else agree to meet the plane on the other end in SF.
Another option would be simply to pay for places on a jet making the trip for both owner and pet. If you are flexible about when to travel, this could be reasonably economical. Check with the charter companies; http://www.jetsuite.com/suiteshare
is another approach.