ProjectLaravel/app/Models/Route.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class Route extends Model
{
    use HasFactory;

    public function departure_airport() {
        return $this->belongsTo('App\Models\Airport');
    }

    public function arrival_airport() {
        return $this->belongsTo('App\Models\Airport');
    }
}