 The F-14D variant was developed at the same time; it included the GE F110-400 engines with newer digital avionics systems such as a glass cockpit, and compatibility with the Link 16 secure datalink.The Digital Flight Control System (DFCS) notably improved the F-14's handling qualities when flying at a high angle of attack or in air combat maneuvering.While the F-14 had been developed as a lightweight alternative to the F-111B, the F-14 was still the heaviest and most expensive fighter of its time.