Using internal mag from pixhawk when far from powerline

When my pixhawk is mounted 25cm away from any high power cable (motor-lipo-bec), is it ok to use the pixhawk internal magnetometer? Or should I definitely go for an external mag? The motors are even further away - aprox 35cm distance.
There is only a 2.4ghz antenna 12cm before the pixhawk, and I think, this is not a problem so far.
Are my assumptions correct? At least on mission planner, the heading doesnt look so bad.

For plane the internal should be fine. You are posting in the plane section so I assume it’s not a copter. Then again, you said motors plural, so it could be a copter unless you are flying a twin. For a copter I would definitely use an external mag.

Yes its a plane with twin motors ! Thank you for helping me