I have a 433 MHz Telemetry for my plane, Is there a way to increase it's range to 10+kms . I currently use a stock antenna.

Even with a better antenna you're unlikely to get 10 km on the standard 433 MHz modules that come with clone APM/ Pixhawk bundles. If you really want long range people typically use the RFD900 module

Okay thanks

But where to get one and is it legal in India

You could buy one from jdrones.com, I don't think it's available in India. You could buy the CUAV radios from aliexpress as well. All of these systems cost upwards of 200$ for the ground and air unit combined.

But bro , indian mobile networks work on 900 MHz , does it cause interference?

There must be a 433mhz version. You should check. I am not sure. You could contact Topalle on this forum. He must be using one for the UAV outback challenge.

Regards
Nitesh

Thanks