The original plane...

object(Airplane)#1 (2) {
  ["model"]=>
  string(9) "Piper Cub"
  ["color"]=>
  string(6) "silver"
}

Upgrading the fleet...

object(Airplane)#1 (2) {
  ["model"]=>
  string(23) "McDonnell Douglas DC-10"
  ["color"]=>
  string(6) "silver"
}

Cloning the plane...

object(Airplane)#2 (2) {
  ["model"]=>
  string(23) "McDonnell Douglas DC-10"
  ["color"]=>
  string(20) "Red, White, and Blue"
}