Line 3 (Cyan Gray Line) will have MTR's CAF-Train solely as the rolling stock. Line 3 is running specially configured 6-car trains instead of the original 8-car arrangement. Therefore, the original 12 trainsets running on Tung Chung Line (TCL) and 11 trainsets running on the Airport Express (AEL) need reforming to get the 23 desired trainsets.
| Car Formation of CAF-Trains after reformation | |||||
|---|---|---|---|---|---|
| ← To West Lake & Mita-Shiro | To Llanmara & Airport → | ||||
| V3xx(odd) - Z3xx(odd) + G3xx(odd) - F3xx (odd) + Z3xx(even) - V3xx(even) | |||||
| xx refers to any number from 01 to 46 | |||||
| Car Prefix | Driver's Cabin | Pantograph/ Engine1) | Motor | Cyan Car (Premium class / coach seats) | Automatic Coupler | 
| V3xx | O | O | O | X | X | 
| Z3xx | X | X | O | X | O | 
| F3xx | X | X | O | O | O | 
| G3xx | X | O | O | O | O | 
There are in broad 3 types of reformation, named Type A, Type B and Type C. Types A and B are further split into Type A1, Type A2, Type A3, Type B1 and Type B2.
| Original Car Number | Change(s) | New Car Number | 
|---|---|---|
| Type A1 | ||
| TCL V8xx | No Change | V3xx (odd) | 
| TCL Z8xx | No Change | Z3xx (odd) | 
| AEL H2xx | No Change | G3xx (odd) | 
| AEL F2xx | Install automatic coupler | F3xx (odd) | 
| TCL W6xx | Install automatic coupler | Z3xx (even) | 
| TCL V6xx | No Change | V3xx (even) | 
| Type A2 | ||
| TCL V8xx | No Change | V3xx (odd) | 
| TCL Z8xx | No Change | Z3xx (odd) | 
| AEL E1xx | Rotate 180° Uninstall driver's cabin | G3xx (odd) | 
| AEL F1xx | Install automatic coupler | F3xx (odd) | 
| TCL W6xx | Install automatic coupler | Z3xx (even) | 
| TCL V6xx | No Change | V3xx (even) | 
| Type A3 | ||
| Similar to Type A1, but the inverter is changed to Siemens SIBAC IGBT VVVF | ||
| Type B1 | ||
| AEL K4xx | Install windows Remove luggage racks, install lateral seats and poles | V3xx (odd) | 
| AEL J4xx | Change to TCL like configuration: Change 3 windows to 3 doors forming doors 1, 3, 5 Change coach seats to lateral seats and install poles | Z3xx (odd) | 
| AEL E1xx | Rotate 180° Uninstall driver's cabin | G3xx (odd) | 
| AEL F1xx | Install automatic coupler | F3xx (odd) | 
| TCL W7xx | Install automatic coupler | Z3xx (even) | 
| TCL Y7xx | Install driver's cabin | V3xx (even) | 
| Type B2 | ||
| Similar to Type B1, but the inverter is changed to Siemens SIBAC IGBT VVVF | ||
| Type C | ||
| AEL K4xx | Install windows Remove luggage racks, install lateral seats and poles | V3xx (odd) | 
| TCL W7xx | Install automatic coupler | Z3xx (odd) | 
| TCL Y7xx | Change to AEL like configuration: Change doors 1, 3, 5 to windows Change lateral seats to coach seats and remove some poles | G3xx (odd) | 
| AEL J4xx | No Change | F3xx (odd) | 
| TCL W7xx | Install automatic coupler | Z3xx (even) | 
| TCL Y7xx | Rotate 180° Install driver's cabin | V3xx (even) | 
| Trainset After | Date Start Test Run | Date Start Service | Trainset Before | Reformation Type | |||
|---|---|---|---|---|---|---|---|
| 1 | V301/V302 | V604/V804 E103/K403 | A1 | ||||
| 2 | V303/V304 | V604/V804 E103/K403 | B1 | ||||
| 3 | V305/V306 | V611/V811 V612/V812 E111/K411 | C | ||||
| 4 | V307/V308 | V608/V808 E105/K405 | B1 | ||||
| 5 | V309/V310 | V611/V811 V612/V812 E111/K411 | A1 | ||||
| 6 | V311/V312 | V611/V811 V612/V812 E111/K411 | A2 | ||||
| 7 | V313/V314 |  | |||||
| 8 | V315/V316 |  | |||||
| 9 | V317/V318 | V608/V808 E105/K405 | A1 | ||||
| 10 | V319/V320 |  | |||||
| 11 | V321/V322 |  | |||||
| 12 | V323/V324 |  | |||||
| 13 | V325/V326 |  | |||||
| 14 | V327/V328 |  | |||||
| 15 | V329/V330 |  | |||||
| 16 | V331/V332 |  | |||||
| 17 | V333/V334 |  | |||||
| 18 | V335/V336 |  | |||||
| 19 | V337/V338 |  | |||||
| 20 | V339/V340 |  | |||||
| 21 | V341/V342 |  | |||||
| 22 | V343/V344 |  | |||||
| 23 | V345/V346 |  | |||||