You may already know but just to clarify SongBird never went through the process to add a B767 for their certificate. Any type aircraft added to a Part 121 certificate requires aircraft specific flight, maintenance, ramp, attendant manual approval. Table top exercises. A partial evacuation and ditching demonstration, a few proving runs and ETOPS approval for Oceanic operations, North Atlantic and/or Pacific. Still much less paperwork and cost due to already having an existing certificate. Several months ago when I checked the leases on the B777 were about twice that of a B767-300.