Upvote:1
www.adioso.com has fairly flexible searches where you can float dates and set regions as destination. Example DUS <-> DEL is US$ 896 depart 12/23, return Jan 4. This is probably as good as it's going to get: It's Christmas time with many people being off work, so flight prices are very high during that time
Upvote:5
For the flexible date and region search option you should try Kayak which provides flexibility of date via Month and shows map of region for destinations as shown below.
Also, you can try ITASoftware (this provide you a calender view where you can see the cheapest fare, but you will not be able to book using this site, so after your results go to another site and book from their with provided details).
Other than these some sites like Orbitz provides flexible date and airport search within some distance as entered by you and MakeMyTrip provides some instant suggestion on flexible dates once you have made search.
These are MakeMyTrip images