private void CheckAirplane()
 {
     foreach (var x in Airplanes.Include(x => x.Company))
     {
         Console.WriteLine($@"id:{x.AirplaneId},  name:{x.Manufacturer}  {x.Model},   country:{x.Company.Name}");
     }
 }
        private void ShowStats()
        {
            Console.WriteLine("===============Air companies============");
            foreach (var x in Companies.Include(a => a.Airplanes))
            {
                Console.WriteLine(
                    $"\n\nname:{x.Name}, country:{x.Country}\nAirplanes\n{string.Join('\n', x.Airplanes)} ");
                if (x.Airplanes == null)
                {
                    x.Airplanes = new List <Airplane>();
                }
            }



            Console.WriteLine("===============Airplanes============");
            foreach (var x in Airplanes.Include(a => a.Trips))
            {
                if (x.Trips == null)
                {
                    x.Trips = new List <Trip>();
                }
                String trips = x.Trips.Count == 0 ? "No flights planned" : $"{string.Join('\n', x.Trips)}";
                Console.WriteLine(
                    $"id:{x.AirplaneId}, company:{x.Company}, {x.Manufacturer}-{x.Model}\nTrips\n{trips}");
            }
        }