139 USSD: It means Unstructured Sequential Supplementary Data.

The communication held in this mode is based on sessions and is interactive. The customer dial *139# from any operator hand held device. The display message shows- Welcome to Railway Enquiry Service

Following Rail enquiry services are displayed immediately:
  1. PNR Enquiry
  2. Arr/ Dep Enquiry
  3. Seat Availability
  4. Fare Enquiry
  5. Train Name/ No. Enquiry
  6. Train Time Table
  7. Locate Train
The customer presses the desired menu button and receives all the information via response display message on screen and a SMS.