Airtel has recently launched Huawei Modem with Latest Custom Firmware 21.157.13.00.284. When you see in modem printed, you will get Huawei E1731 only. But when you see the inner side, then you will get Huawei 173Cs-1. Huawei E173Cs-1 firmware is different from the previous one before this Airtel has launched a modem with Custom Firmware version 11.126.16.04.284, which is not unlocked in the market. Because hackers could not unlock still Firmware 21.157.13.00.284. The Hardware version of Airtel E173Cs-1 is CH2E303SM. Still, we have a firmware flasher that works with this modem and upgrades it to 21.157.13.00.910.B757. When you flush, then you will be asked for a flash code. You can download Universal master code and just run this.
Put your modem IMEI Number in the Huawei tab and click on the Calculate button. Now you will get the Unlock code and Flash code. When you flash your modem, it will ask for a code, then provide a flash code.
Now put another SIM in your modem and connect to your laptop/PC. It will ask for an unlock code. You have already got an unlock code for your modem through Universal master code. Please don’t use it, because it will not accept it. This software generates unlock codes for 35 series IMEI number, but if will see your modem inside you will get the 86 series IMEI number. I have got an unlock code generator for 86 series IMEI numbers. You can see at below link.