How to calculate an orbit around the earth with respect to Mercator projection? - three.js

Question

I'm trying to create a small interactive UFO-flying-around-the-earth scene in three.js.
I thought it would be good to control the UFO on a 2D projection of the map (like a minimap), convert the pixel coordinates to lat/lng coordinates and finally transform lat/lng to a Vector that I can use for my 3D scene.
As it turns out, it wasn't.
Works great if the UFO flies around the Equator (+/- some degrees), but for sure I forgot to apply the projection to my 2D controls:
Now I'm a little bit lost. My controls (WASD keys) basically sets the speed and the rotation of the UFO on the minimap, but I have to add some sort of "correction" to the player. That's how the values are set at the moment:
let left = parseFloat(this.minimapPlayer.style.left) + this.speed * Math.cos(Math.PI / 180 * this.rotation)
let top = parseFloat(this.minimapPlayer.style.top) + this.speed * Math.sin(Math.PI / 180 * this.rotation)
Is there a way to create a "real" orbit, so that my UFO doesn't always fly through both poles? Or may there be a better approach to handle the orbit of the UFO (maybe without the minimap)?
Here's the full animation code so far:
animatePlane(firstRender) {
requestAnimationFrame(this.animatePlane)
// set next position
let left = parseFloat(this.minimapPlayer.style.left) + this.speed * Math.cos(Math.PI / 180 * this.rotation)
let top = parseFloat(this.minimapPlayer.style.top) + this.speed * Math.sin(Math.PI / 180 * this.rotation)
// handle border collisions
if (left < 0) {
left = this.minimapBounds.width
}
if (left > this.minimapBounds.width) {
left = 0
}
if (top < 0 || top > this.minimapBounds.height) {
this.rotation = this.rotation * -1
if (this.rotation > 0) {
this.plane.up.set(0, 1, 0)
} else {
this.plane.up.set(0, -1, 0)
}
top = top + this.speed * Math.sin(Math.PI / 180 * this.rotation)
if (left < this.minimapBounds.width / 2) {
left = left + this.speed * Math.cos(Math.PI / 180 * this.rotation) + this.minimapBounds.width / 2
} else {
left = left + this.speed * Math.cos(Math.PI / 180 * this.rotation) - this.minimapBounds.width / 2
}
}
this.minimapPlayer.style.left = `${left}px`
this.minimapPlayer.style.top = `${top}px`
// convert to lat/lng
const lat = (180 / this.minimapBounds.height) * (top - this.minimapBounds.height / 2) * -1
const lng = (360 / this.minimapBounds.width) * (left - this.minimapBounds.width / 2)
// convert to vector
const p = this.latLongToVector3(lat, lng, this.radius, 200)
this.plane.position.set(p.x, p.y, p.z)
// bottom of the plane should always look the the middle of the earth
this.plane.lookAt(new THREE.Vector3(0,0,0))
}