A few years ago I paid a visit to Linear Air, a small start-up just outside Boston that hoped to make a go of it as an air-taxi operator. CEO Bill Herp figured there had to be a better solution for business flyers than the way the airlines did it. The idea was to fly Eclipse jets, as soon as they could, but meanwhile they got Linear Air up and running using Caravans, as a sort of test phase.Well, it’s no surprise, the Caravans have done just great. They’re reliable, comfortable, and for getting the kids, nanny, golf clubs and family dog to Nantucket for the weekend, they certainly beat out the Eclipse jet.The fact is that NASA’s Small Aircraft Transportation System concept — using under-utilized local airports, avoiding the hub-airport congestion, and offering concierge-style service — is hard not to like. Modern software makes it more manageable and more profitable than the old air-taxi model, from decades back, when the random passenger called around looking to hire a small airplane off the flight line.But maybe the VLJ is not the critical asset to make this work. Take a modern turboprop like a Caravan or a TBM or Pilatus, and park it next to the last-century light twins that used to form the bulk of the air-taxi fleet, and there’s no comparison. The leap from these modern turboprops to the new VLJs is a much smaller one — in overall performance, point-to-point, some of them are virtually even. To most passengers, the difference is probably insignificant. Operating costs are more complex to compare, but Linear Air seems to thrive with its Caravan fleet, while DayJet is struggling to get by with the theoretically-economical E500s.A week or so ago, SATSAir, another small operator out of South Carolina, reported that it’s making a go of it with Cirrus SR22s. SATSAir launched 16,000 flights last year, a 60 percent surge over the year before. The company has flown more than six million passenger miles since November 2004, all of them behind a prop. The service itself is what makes it work, not the powerplant.No question, though, there is a preference out there among the masses for jets. When I visited Linear Air, I asked if they really needed the Eclipse jets, or why not just add more Caravans. Oh yes, they said, passengers call and ask when the jets be available, and they don’t want to fly on a prop plane. But then, that was before they realized they’d have to leave their baggage on the ramp. No problem for a business flyer going to a meeting, with a Blackberry and a briefcase. But for those pile-’em-in golfing weekends, the VLJs might have to make room for a lot of other options in the next-gen air-taxi world.