plz speak up
That is true, you have to block the ticket , any flight booking agent will help you on this.
Its free of cost, however there is some time period for this, before that you have to confimr or Cancel the ticket.
I'd suggest that you block at least 2 tickets of diferent dates so as to minimize the risk.
Also a good news, If you book AIR-INDIA flight and if VISA is not received till that date/get rejected (which is not going to happen in your case, you will get it soon) then you will not have to pay a single penny, you will be eligible for 100% refund, just call AIR-INDIA customer care to get more information on this.
Also in case if you have to cancel ticket after getting VISA (coz of some reason) then they will charge 5000 INR and will refund remaininig amount, again I'd suggest to talk to AI cust care.
Hope this is helpful.
so you have 2 options now ( I guess
1. block ticket using Agent
2.book on your own
Best of luck for your VISA.