First I want to thank you Bac9 for creating the most awesome pack of parts, one that fits perfectly my "Why go to space if it's not with style" kind of mind. But I have to admit I found some of the engines a bit too efficient. Here's why: There you can see my newest VTOL, a true marvel of balancing if I may, very easy to fly, take off and land perfectly, I love it! It's a jet only plane, no oxidizer, but I almost reached orbit (100km x 51km), and the engines are still running (although at an extremely low power). You can also notice that I was in flight for 23minutes and still near full tank. So I thought "Damned, I'm sooooo close, all I need is a dozen of m/s!" That's when I noticed that my compressed air thrusters where still full... And here you have it: Orbit achieved on air breathing engine only! Anyway, it's still a great mod!