Short answer
Book four to six months ahead for international travel, and eight months for peak dates such as Christmas, Diwali or the May–June school break. For Europe the binding constraint is the visa appointment, not the flight. International airfares from India are usually cheapest 90 to 150 days before departure.
Different destinations have different bottlenecks, and identifying yours decides the lead time. For Europe it is the VFS or BLS appointment, which runs six to ten weeks out in peak season. For the Maldives and Bali it is the villa inventory, which is small. For an African safari it is the camp, where a good Mara conservancy camp sells out ten months ahead for August.
Airfare behaves separately. Fares from Indian metros to long-haul destinations bottom out roughly 90 to 150 days before departure and climb steadily inside 45 days. Booking twelve months ahead does not usually save money on the flight; it saves the hotel and the visa slot.
The one thing to sequence correctly: hold flights rather than buying them until the visa is approved. Airlines and consolidators will hold a fare for 24 to 72 hours, and most consulates accept a reservation. Buying a non-refundable ticket before approval is how a refusal turns into a $1,000 loss.
| Trip | Lead time | The binding constraint |
|---|---|---|
| Europe, June–August | 6–8 months | Schengen appointment availability |
| Maldives or Bali, December–January | 7–9 months | Villa inventory over the New Year peak |
| Masai Mara, August–September | 9–12 months | Conservancy camp beds during the migration |
| Kashmir tulip season, April | 5–6 months | Srinagar houseboats and airfare spike |
| Dubai or Thailand, off-peak | 2–3 months | Nothing binding; price is the only factor |
| Char Dham Yatra, May–June | 5–6 months | Kedarnath registration slots and helicopter seats |