Hi there, welcome to the forum!
The cheaper flights from Chennai to Port Blair begin at November 17 onwards. But once December sets in, the fares reach the Rs. 7,000 mark again. So if your schedule allows you to, book flights this November. If ever you cannot make it this month, you can try the months of March to May. These months are off-peak season but the temperatures can be very hot and humid. Thus, your best option would still be the month of November, when flights aren't too expensive and the temperatures in the Andaman Islands aren't high. There won't be as much crowds as well.
Affordable Flights from Chennai to Port Blair
November 18, 2016
| Airline Name | Flight Number | Departure | Arrival | Fare |
| Indigo | 6E 188 | 8:45 | 11:15 | Rs. 5,322 |
| Go Air | G8 305 | 8:15 | 10:30 | Rs. 5,325 |
| Jet Airways | 9W 613 | 11:40 | 13:50 | Rs. 5,749 |
| Spice Jet | SG 608 | 12:05 | 14:15 | Rs. 5,959 |
November 27, 2016
| Airline Name | Flight Number | Departure | Arrival | Fare |
| Indigo | 6E 188 | 8:45 | 11:15 | Rs. 4,900 |
| Go Air | G8 305 | 8:15 | 10:30 | Rs. 5,270 |
| Jet Airways | 9W 613 | 11:40 | 13:50 | Rs. 4,636 |
| Spice Jet | SG 608 | 12:05 | 14:15 | Rs. 4,474 |
November 28, 2016
| Airline Name | Flight Number | Departure | Arrival | Fare |
| Indigo | 6E 188 | 8:45 | 11:15 | Rs. 4,792 |
| Go Air | G8 305 | 8:15 | 10:30 | Rs. 5,270 |
| Jet Airways | 9W 613 | 11:40 | 13:50 | Rs. 4,636 |
| Spice Jet | SG 608 | 12:05 | 14:15 | Rs. 4,474 |
So these are all the flights with most affordable fares this month. As you can see, November 18 has flights with fares ranging from Rs. 5,322 to Rs. 5,959. These flights don't have long waiting times too. There are other more expensive flights still so do take note of the number of these flights. November 27 and November 28 has the cheapest flights ranging from Rs. 4,474 to Rs. 5,270.
When it comes to the luggage allowances, it's mostly the same for all airlines. As you would see on the following table:
Domestic Flights Baggage Allowances
| Airline | Cabin Baggage Allowance (Weight) | Cabin Baggage Allowance (Dimension) | Checked Baggage Allowance (Weight) | Checked Baggage Allowance (Dimension) |
| Indigo | 7 kilograms, 1 piece | 115 centimetres | 15 kilograms | 158 centimetres |
| Go Air | 7 kilograms, 1 piece | 115 centimetres | 15 kilograms (Go Smart & Go Flexi)
35 kilograms (Go Business) | 158 centimetres |
| Jet Airways | 7 kilograms, 1 piece | 115 centimetres | 15 kilograms (Standard)
20 kilograms (Silver)
25 kilograms (Gold)
30 kilograms (Platinum) | 158 centimetres |
| Spice Jet | 7 kilograms, 1 piece | 115 centimetres | 15 kilograms | 158 centimetres |
So while these flights are the cheapest, there isn't much difference in the baggage allowances. In Go Air and Jet Airways though, you can upgrade for a higher seat so you can avail of the bigger baggage allowances. But then, you'd also have to pay higher in terms of fare.
I hope this helps you.
