phpvms/app/Http/Resources/Flight.php

<?php

namespace App\Http\Resources;

use App\Support\Units\Distance;
use Illuminate\Http\Resources\Json\Resource;

class Flight extends Resource
{
    /**
     * Set the fields on the flight object
     *
     * @return array
     */
    private function setFields()
    {
        $fields = [];
        foreach ($this->field_values as $field) {
            $fields[$field->name] = $field->value;
        }

        return $fields;
    }

    public function toArray($request)
    {
        $flight = parent::toArray($request);

        $flight['ident'] = $this->ident;

        // Return multiple measures so the client can pick what they want
        if ($this->distance instanceof Distance) {
            $flight['distance'] = $this->distance->units;
        }

        $flight['airline'] = new Airline($this->airline);
        $flight['subfleets'] = Subfleet::collection($this->subfleets);
        $flight['fields'] = $this->setFields();

        return $flight;
    }
}