The extra 4 ft ( 1.2 m ) of length was added behind the first body - side porthole .
The extra 4 ft ( 1.2 m ) of length was can be recognised by the greater distance between that porthole and the first small carbody filter grille .
The extra 4 ft ( 1.2 m ) of length was added behind the first body - side porthole , and can be recognised by the greater distance between that porthole and the first small carbody filter grille .