If you look at the Citation Excel series, you can clearly see that two other Citation models have been combined. The nose and forward fuselage are of the Model 750 Citation X, initially with the blunt nose of the Citation III. The wings and tail come from the Cessna 560 Citation Encore. Also the engines are of the same family as the Encore. The nacelles have long fairings for the thrust reversers. Typical for the Model 560XL are the ventral fins below the horizontal stabiliser.

The different versions of the Cessna Model 560XL are distinguished by

• the shape of the nose
• the number and shape of the cockpit windows

The first version of Model 560XL is the Citation Excel. It is as described above, with a blunt nose. The aircraft got a facelift in 2003 and that became the Citation XLS. However, nothing changed on the outside, only on the inside. 

Starting with the Citation XLS+ more changed. Apart from FADEC engine controls and improved PW545C engines, the XLS+ also has a more pointed nose than the Excel and XLS, and is much like that of the Citation X and Citation Sovereign.

The Citation XLS Gen2 can be distinguished by lighted air stairs and a different curtain, both which can only be seen when the door is open. Other changes are in the cabin.

While the previous Models 560XL still had the nose and cockpit windows of the Cessna 750, this has changed on the Citation Ascend. This version has four cockpit windows very similar to those on the Citation Latitude. Additionally, the oval cabin windows are more rounded