I just played Airport CEO again after a couple of months and I thought it would be good to start again and play along with the tutorial for the beginning. At the last stage of the 1. tutorial, I should buy a fuel truck, but I didn’t find it under economy after a bit of search through the menu I found the purchasing site and could buy the truck. I think you should change this in the tutorial. (I’m playing in German so I don’t know if it’s just not translated yet.)
I’m sorry if this was reported latley, but I hope I could help.