I sent a plane into orbit with a kethane scanner and found a decent amount of kethane on the continent north of the Space center. I rig up a plane with conventional engines a couple kethane tanks, and a drill and fly it over to the site pulling a perfect landing.
I plant a flag marking the site and drill til the kethane tanks are full. I have some difficulty taking off again, but didn't think anything of it, blaming it on the uneven terrain. When I get back to KSC do I see the mistake. The plane is now very front heavy. It flies but I load many quicksaves trying to land the thing. It can't stay level enough to touch down softly anywhere under 200m/s, and 200m/s is fast enough that the plane flips and bounces when landing.
After the 12th or so try I manage to land in the grass near the tracking station, (the idea of landing the flying brick on the runway is absurd at this point) I congratulate myself and carefully taxi the plane back to the start of the runway where my kethane storage tank is, empty the plane's tanks and look to check out my progress towards filling the tanks.
It was at that point where I died inside. After converting the kethane into liquid fuel to refill the jet I actually did all that for a kethane profit of a little over 1000.
KSP Kethane mod