Antenna Simulation on A/C

Hello

I have designed 2 patch antennas that behave quite well in FEKO.

Then I put them on the aircraft 3D model and try to mesh the A/C model at desired frequency that is several GHz.

The amount of meshed elements on the A/C body is about 6 millions and solver is not capable of solving it, since its stacked in its first step for several hours

What are possible ways to overcome this issue?