This question has always perplexed many of our defence analysts. They've always raised the questions as to why India prefers to operate twin seat variants of Fighters. However, this assumption is not always true. India has operated the Single seat fighters in Mirage 2000, Tejas, Mig 29, even MiG 21. So, why some twin seaters and some single seaters?
Traditionally it has got to do with the current fleet composition and future procurement plans. Also, the aircraft with IDS (air Interdiction and Strike) capabilities have been twin seaters.
Let us revisit the trends.
The examples stated above are Su-30 MKI, MRCA and FGFA.
If you notice, all these aircraft had not been designed only with Air-superiority in mind. This, in part, is because of the versatility of their platforms. They are also designed to undertake SEAD and DEAD missions (SEAD stands for Suppression of Enemy Air Defences and DEAD stands for Destruction of Enemy Air Defences). These aircraft will be deployed by IAF on the Day 1 of the conflict. Their role will not be to just establish air-superiority but also sustain Air-superiority. This essentially means loitering around in the hostile airspace and shooting down oncoming enemy fighters while protecting our own strike aircraft. Under such demanding situations, having a two man crew is not just essential but more than helpful. While the pilot takes care of flying the platform and carrying our evasive manoeuvres to escape enemy SAMS and AAA, the WSO who sits in the back operates the ECMs and Weapons locking and deployment. However, it is the pilot who launches the weapon and employs flares and chaff after weapon launch. Also, the WSO maintains constant communication link with Ground Stations and nearby AWACS... This removes the pressure of the pilot who can concentrate on flying the aircraft in such a demanding situation and returning the crew back safely out of the hostile airspace. It also helps when you have a fellow warrior behind you.
Then, you may conjure as to why do we operate Single seat MiG 29s and LCAs. These are designed to defend the Indian skies from any invading aircraft. They never leave the Indian airspace unless deemed utmost necessity. In fact, they are optimised for BVR combat so that they enemy aircraft can be shot at even before it enters our sky.
This planning of our fleet can even be noticed by observing the airbases. The MiG 29s are never operated from any of the eastern airbases of India. They only operate on the western flank of india . Why? Because, in any future war, against Pakistan India will just operate BVR fighters to maintain a high strike rate against Pakistani F16s. But against the Chinese, India will try to carry out surgical strikes deep inside Chinese territory to take out the airfields of Tibet. Here, the unique features and capabilities of Su-30MKI will be more suited for the role than single seaters. If my guess is right, the Rafale (if inducted) will also be operated exclusively from the eastern airbases and northeast bases.
P.S: sorry if my answer veered out of topic.
Twin seat fighters of IAF:
1.Mirage 2000TH/TI : Total 9 in service
2. Mig-29UPG
3. Jaguar
4. Su-30MKI & Mig-21UM
5.Upcoming RAFALE-DH