score:8
You don't need ID to book a flight unless you're physically at an airline counter or travel agent. And even then, you just need any valid ID, not necessarily a Passport.
The ticket must be issued in the name that matches your Passport/ID.
You only need a valid Passport or other travel docs to actually travel. Meaning, enter the airport terminal and board the aircraft.
It is vary common for new travelers to book travel while awaiting a new Passport. However, be aware that if you or your companion are unable to obtain a Passport before departure, the airline is not obligated to refund any non-refundable fare.
Upvote:2
Most websites don't ask for your passport details at booking time, so all you need to know in advance are the names of all the passengers traveling on the ticket you're purchasing. Otherwise you can type in whatever random information you want into the passport-related fields as the airline never verifies those details when you get to the airport.
Just make sure you have a passport for the day of the actual flight as India doesn't accept European ID cards for entry.