You can get quick answer of your question by entering here
What are the extra parameters we need to pass for Special fare booking like Student fare, Arm force, Senior citizen fare in flight API?
In case of special fare(Student fare, Arm force, senior citizen fare etc..), you must pass 2 more parameters "DocumentType" and "DocumentId". These fare types are applicable for both LCC and GDS and valid for international flights as well. Please refer to the below flight document:
API Docs: https://www.srdvtechnologies.com/doc/flight/v8/ticket-lcc