“It would’ve been a massive inconvenience for other travelers at airports and make campaign scheduling impossible if he didn’t use a private jet.”
No it wouldn’t. I flew in first class with a famous presidential candidate aboard a Delta flight coming back from Italy. He was the last to board (he apparently had VIP accommodations at the airport since he wasn’t in the first class lounge) and the first to leave the plane and no one bothered him the entire trip (I was sitting one row behind him) although as we were leaving many of us wished him well. I think 95% of the people on the plane didn’t even know he was aboard. He was met by NYC police at the door of the plane, and I walked right behind him off the plane and all the way to the JFK customs line where he was met and went through a separate entry.
For 50 people, it might have been not much more expensive to rent the jet.
On certain things I'll defend Sanders. Making an efficient and economically sound financial decision is something I'd expect from him.