On the topic of out of control jet plane with LFEs... you probably know this already but you will want to align thrust vectors on all three possible occasions, a) when only the jets are on, when only the LFEs are on, and c) when all of them are on. you can check all those by setting thrust limit at 0 with tweakables. (you can have some leeway with all three cases, the more gimbalable the engines are the more leeway you've got) You can easily shut all of the LFEs down by forbidding oxidizer usage, it's easier to do most of the time, if you don't have group actions yet. You will also need low atmo torque for your SAS, cause when you are high up the wings are useless, plop some reaction wheels and RCSs on will help a lot. flexible LFEs will also help, making thud one of the best ones for the job (which is why it's kinda weird you couldn't make it work with thud) Finally you need to be aware that burning fuel will change your center of mass, which could bungle everything up, set your fuel storage to zero with tweakables and check if that would put your center of lift ahead of your center of mass, and make sure that it doesn't. Back to your,.. already answered... question, the most powerful use of the basic jet engine is that it allows you to do surface surveys, which is really handy because those tend to come in couples, giving your jet planes a really high ROI, esp. on science points. If the target is close you can just fly there, if it's more than a quarter away around Kerbin ... well, you either need to be real patient, or you can put a jet plane on a rocket. The important thing is you will be able to precision land once you are back in the atmosphere. P.S. I do all of my "in flight" contracts with orbital dropped drones, those targets have a very huge margin so it's rather easy to get the drones into range, but the surface contracts are rather specific with your location, again, making the basic jet useful. - - - Updated - - - It's a lot easier to climb via control surfaces, you could have 2 pairs aft for pitch control that doubles as a ladder You can also make your craft "sit down" with the retractable landing gears if you researched 'landing' before 'space exploration'