AJ's right, you need to do it with forced perspective, with nly one viewpoint.. In other words, a shadow box diorama...
Depending on what you want to do, put the A-10 in the rear or the tank, that will determine what scales you're going to use.. If you want the A-10 approaching from the rear (I'd suggest the rear quarter, either the 5 O'clock or 7 O'clock to the tank), then you'll probably want the A-10 in 1/144 scale and the tank in a larger scale, either 1/48 or 1/35th, with the tank right at the front...
Flipped around, you could do the A-10 in 1/72 or 1/48, with the tank at the plane's 12, but coming in at the rear quarter again on the tank.. You could also show the A-10 after the pass, with the pilot standing it up on one wing as he banks hard to come around again.. That'll show the viewer the entire top of your A-10..
Here's and example of a shadow box dio, using forced perspective:
The Mustang is 1/48th, the Me262 is 1/72..
At any rate, it sounds like you got your work cut out for you..
Keep us posted!